Method for manufacturing electrode for fuel cell

ABSTRACT

A fuel cell electrode is proposed which has a positive electrode layer ( 20 ), a negative electrode layer ( 19 ) and an ion exchange film ( 21 ) interposed between these. Before a solution for making one of the other of positive and negative electrodes has dried, a solution for making the ion exchange film is applied to it, and then a solution for making the other electrode is applied while the solution for making the ion exchange film is not yet dry. Because the layers are not dry, the intimacy of the layers improves. By the ion exchange film being made a solution, the applied film can be made thin.

TECHNICAL FIELD

This invention relates to a method for manufacturing an electrode foruse in a fuel cell which has an ion exchange film disposed betweenpositive and negative electrodes and generates electricity by hydrogenbeing brought into contact with a catalyst in the negative electrode andoxygen being brought into contact with a catalyst in the positiveelectrode.

BACKGROUND ART

FIG. 33 and FIG. 34 hereof show a fuel cell electrode of related art. Inthis fuel cell electrode 700, an ion exchange film 703 is disposedbetween a negative electrode layer (hydrogen electrode) 701 and apositive electrode layer (oxygen electrode) 702, and an electricalcurrent is generated by a hydrogen molecules (H₂) being brought intocontact with a catalyst included in the negative electrode layer 701 andoxygen molecules (02) being brought into contact with a catalystincluded in the positive electrode layer 702 to cause electrons e⁻ toflow as shown by the arrow. In the generation of the current, water(H₂O) is produced from the hydrogen molecules (H₂) and the oxygenmolecules (O₂).

As shown in FIG. 34, the fuel cell electrode 700 has binder layers 706,707 on the respective inner sides of a pair of diffusion layers 704,705. These binder layers 706, 707 have the negative electrode layer 701and the positive electrode layer 702 on their inner sides. The ionexchange film 703 is positioned between the negative electrode layer 701and the positive electrode layer 702.

To manufacture this fuel cell electrode 700, first a solution for makingthe binder layer 706 is applied to the diffusion layer 704, a solutionfor making the binder layer 707 is then applied to the diffusion layer705, and then by the applied binder layers 706, 707 being fired, thebinder layers 706, 707 are hardened.

Next, a solution of the negative electrode layer 701 is applied to thehardened binder layer 706, a solution of the positive electrode layer702 is applied to the hardened binder layer 707, and by the appliednegative and positive electrode layers 701, 702 being dried, thenegative and positive electrode layers 701, 702 are hardened.

Then, an ion exchange film 703 in the form of a sheet is placed on thehardened negative electrode layer 701 and the diffusion layer 705 withthe positive electrode layer 702 hardened on it is placed on the ionexchange film 703 to form a 7-layer laminate, after which this laminateis heated and compressed as shown by the arrow to form an electrodestructure.

Because, as mentioned above, in the fuel cell electrode 700 a sheet isused as the ion exchange film 703, and the heating and compression arecarried out with the respective layers of the binder layer 706, thenegative electrode layer 701, the positive electrode layer 702 and thebinder layer 707 each hardened, there is a risk of areas of defectiveintimacy arising at the interfaces of the layers.

When areas of defective intimacy arise in the layers of the fuel cellelectrode, it becomes difficult for a current to be generatedefficiently, and at the inspection stage of the production line theseelectrodes are disposed of as waste or are repaired, and this has beenan impediment to raising productivity.

Also, because a sheet is used as the ion exchange film 703, when thehandlability of the ion exchange film 703 is considered, the ionexchange film 703 must be made somewhat thick. Consequently, it isdifficult to make the electrode thin, and this constitutes an impedimentto making the fuel cell compact.

Thus, there has been a need for it to be possible to prevent areas ofdefective intimacy arising at the interfaces, also for it to be possibleto prevent performance deterioration of the ion exchange film, andfurther for it to be possible to make the ion exchange film thin.

Among these positive and negative electrodes of fuel cells, there arethose which, to suit the application, are polygonal (for example,octagonal).

FIG. 35A and FIG. 35B are views showing a method for forming a polygonalion exchange film of a fuel cell of related art, and illustrate anexample of applying an ion exchange film 703 to a negative electrode701.

In FIG. 35A, a polygonal (octagonal) negative electrode 701 is made ofcarbon paper, and this negative electrode 701 is placed on a table 715.Then, a screen printer 716 is moved from one side 715 a toward the otherside 715b of the table 715 as shown with arrows.

This screen printer 716 has leg parts 716 a, 716 a at its ends and adelivery part 716 b extending between the leg parts 716 a, 716 a, andwhen the delivery part 716 b of the screen printer 716 reaches aposition above the negative electrode 701, a resin solution for makingan ion exchange film is delivered through the delivery part 716 b.

In FIG. 35B, when the screen printer 716 moves between a position E1 anda position E2, a slurry (resin solution) for making an ion exchange filmis applied to the negative electrode 701 through the delivery part 716bof the screen printer 716. The slurry 718 applied outside this negativeelectrode is then removed, after which the resin solution on thenegative electrode 701 surface is dried to obtain a polygonal ionexchange film.

When the slurry 718 is applied with the screen printer 716, because theslurry 718 is delivered through the delivery part 716 b while thedelivery part 716 b is moved as shown by the arrows in FIG. 35A, thearea 719 to which the slurry 718 is applied is a rectangle, as shown inFIG. 35B. Consequently, the slurry 718 is applied to a number of excessareas 719 a outside the negative electrode 701 (that is, the corners ofthe rectangle), and it is necessary for the slurry 718 applied to theseexcess areas 719 a to be recovered. This recovery work takes time, andthis has been an impediment to raising productivity.

To secure the performance of the fuel cell, it is necessary for thesurface of the ion exchange film 703 (see FIG. 33) to be made flat.Consequently, when the slurry 718 is applied with the screen printer716, the slurry 718 must be delivered uniformly from the whole area ofthe delivery part 716 b.

However, to deliver the slurry 718 uniformly over the whole area, from arelatively wide part like the delivery part 716b, it is necessary forthe delivery precision of the screen printer 716 to be made very high.Because of this, the equipment cost of the screen printer 716 is high,and this has been an impediment to lowering the cost of the fuel cell.Accordingly, a method for forming an ion exchange film for a fuel cellhas been awaited with which it is possible to prevent slurry from beingapplied to excess areas and an ion exchange film can be formed flatrelatively simply.

FIG. 36A and FIG. 36B are schematic views illustrating another methodfor forming an ion exchange film of a fuel cell of related art.

In FIG. 36A, an electrode plate 714 made by applying a negativeelectrode 701 to a substrate 713 is prepared, and this electrode plate714 is placed on a table 715. Then, before the applied negativeelectrode 701 has dried, the screen printer 716 is moved as shown by thearrow. This screen printer 716 has a delivery part 716 b at its top, andwhen the delivery part 716 b of the screen printer 716 reaches aposition above the electrode plate 714 (the substrate 713 and thenegative electrode 701), a resin solution for making an ion exchangefilm is delivered from the delivery part 716 b.

In FIG. 36B, when the screen printer 716 is moved between a position P1and a position P2, the resin solution for making an ion exchange film712 is applied to the electrode plate 714 (the substrate 713 and thenegative electrode 701) through the delivery part 716b of the screenprinter 716, and the electrode plate 714 is thereby covered with theresin solution 712. Then, this resin solution is dried and an ionexchange film 703 is obtained.

Now, when while the resin solution 712 is applied to the electrode plate714 from the screen printer 716 it is moved from the position P1 asshown by the arrows, a shear force arises at the surface of the negativeelectrode 701 as shown by the arrow a. Also, when the resin solution 712is applied to the electrode plate 714 from the screen printer 716, thenegative electrode 701 is not yet dry.

When a shear force arises as shown by the arrow a at the surface of thenegative electrode 701 like this, there is a risk of a surface layerpart 701 a of the negative electrode 701 shifting under this shearforce. Product units in which the surface layer part 701 a of thenegative electrode 701 has shifted have to be disposed of as waste orrepaired, and this constitutes an impediment to raising productivity.Accordingly, in forming an ion exchange film on an electrode such as anegative electrode, there has been a need to prevent shifting of thesurface layer part of the electrode.

DISCLOSURE OF THE INVENTION

The present inventors discovered that the cause of areas of defectiveintimacy arising between the layers is that when a next solution isapplied after a previously applied film has hardened, this solution doesnot permeate the previously applied film, and defective intimacy arisesas a result.

When accordingly they applied a solution before the previously appliedfilm had dried, they found that the solution permeated the previouslyapplied film and the intimacy of contact rose markedly.

Similarly, they discovered that also when a solution is applied to anion exchange film in the form of a sheet, the solution does not permeatethe sheet-form ion exchange film, and defective intimacy arising as aresult constitutes another cause.

Accordingly, the present invention provides a fuel cell electrodemanufacturing method including: a step of applying a solution for makinga first electrode of positive and negative electrodes of a fuel cell toa sheet to form a first electrode layer; a step of, before thiselectrode layer has dried, applying a solution for making an ionexchange film to this first electrode layer to form an ion exchangefilm; a step of, before this ion exchange film has dried, applying asolution for making the second electrode to the ion exchange film toform a second electrode layer; and a step of hardening the firstelectrode layer, the second electrode layer and the ion exchange film bydrying them.

That is, in this invention, if a solution is employed for the ionexchange film, and solutions for the electrodes and the solution for theion exchange film are each applied in an undried state, mixing occurs attheir interfaces. By this means, because it is possible to prevent areasof defective intimacy arising at the interfaces of the respective layersof the pair of electrodes and the ion exchange film, the reactionefficiency at the ion exchange film can be kept good.

Here, when a sheet is used for the ion exchange film, it is necessaryfor the ion exchange film to be made somewhat thick, to keep thehandlability of the sheet-form ion exchange film good. Consequently, itis difficult to make the electrode structure thin, and this constitutesan impediment to making the electrode structure small.

In this invention, the ion exchange film is made a solution, so that theion exchange film can be handled in the state of a solution. As a resultof the ion exchange film being made a solution, it is not necessary forthe thickness of the ion exchange film to be regulated for handling.Consequently, the ion exchange film can be made thin, and the electrodestructure can be made as thin as possible.

In this invention, preferably, the above-mentioned drying is carried outwithout a load being applied. That is, the solutions for making theelectrodes and the solution for making the ion exchange film are eachapplied in an undried state, and after the solutions are applied theyare dried without a load being applied. By this means, because it is notnecessary for a load to be applied to the ion exchange film, theperformance of the ion exchange film can be prevented from falling dueto loading.

Also, in this invention, preferably, the negative electrode layer isformed below the ion exchange film and the positive electrode layer isformed above the ion exchange film. When the solution for making the ionexchange film is applied to an undried electrode layer, there is a riskof the solution for making the ion exchange film flowing downward underthe influence of gravity and permeating the electrode layer. When thesolution for making the ion exchange film permeates an electrode layer,there is a risk of the voids in the layer being diminished by thepermeating solution. Consequently, in the manufacture of an electrodestructure for a fuel cell, if, of the positive and negative electrodelayers, the positive electrode layer is disposed below the ion exchangefilm, there is the concern that the voids in the positive electrodelayer will be diminished by the solution for making the ion exchangefilm and that it will not be possible for product water produced by theelectricity generation to be efficiently drained through the positiveelectrode side diffusion layer to outside the fuel cell. When productwater cannot be drained efficiently, because optimal supplying of thereaction gases hydrogen and oxygen is impeded, a density overvoltagebecomes high, and it becomes difficult for the electricity generatingperformance of the fuel cell to be kept good.

Here, “density overvoltage” refers to a voltage drop which appears whenthe rate of replenishment and removal of reactants and reaction productsat the electrodes is slow and the reactions at the electrodes areimpeded. That is, the density overvoltage being high means the amount ofthe voltage drop being large. To avoid this, as described above, in thisinvention, the positive electrode layer is provided above the ionexchange film. By disposing the positive electrode layer above the ionexchange film, it is possible to prevent the solution for making the ionexchange film from permeating the positive electrode layer under theinfluence of gravity, and it is possible to prevent the voids of thepositive electrode layer from being diminished by the solution formaking the ion exchange film. As a result, product water produced byelectricity generation can be guided from the positive electrode layerto the positive electrode side diffusion layer and drained well throughvoids in the positive electrode side diffusion layer, and densityovervoltage arising in the fuel cell can be kept low.

The solution for making the positive electrode is preferably applied ina spray state. When the application pressure of the solution for makingthe positive electrode is high, in the application of the solution formaking the positive electrode, there is a risk of the solution formaking the ion exchange film permeating the positive electrode layer.When the solution for making the ion exchange film permeates thepositive electrode layer, there is a risk of the solution for making theion exchange film reaching the positive electrode side diffusion layerand the voids of the positive electrode side diffusion layer beingdiminished by the solution for making the ion exchange film. To avoidthis, by the solution for making the positive electrode being applied ina spray state, it is applied without excess application pressure beingexerted on the ion exchange film, that is, the solution for making thepositive electrode is applied with a minimal application pressure. Byapplying the solution for making the positive electrode without exertingexcess application pressure on the ion exchange film like this, it ispossible to prevent the solution for making the ion exchange film frompermeating the positive electrode layer. Therefore, the voids of thepositive electrode layer are prevented from being diminished by thesolution for making the ion exchange film, and the voids of the positiveelectrode layer can be secured much better. By this means it is possibleto guide product water produced by electricity generation from thepositive electrode layer to the positive electrode diffusion layer anddrain it through voids in the positive electrode side diffusion layermuch better, and density overvoltage arising in the fuel cell can bekept low.

In this invention, the above-mentioned drying is carried out by heatingfrom the insides of the electrodes with far infrared radiation, andexcessive permeation of the solution for making the ion exchange filminto the electrodes is thereby prevented. By thermally drying the firstelectrode layer, the ion exchange film and the second electrode layerusing far infrared radiation like this, it is possible to dry the wholeof the ion exchange film rapidly from its surface to its interior, andpermeation of the solution for making the ion exchange film into thefirst electrode layer and the second electrode layer can be suppressed.By suppressing the permeation of the solution for making the ionexchange film into the electrode layers, it is possible to prevent thevoids in the electrode layers being blocked by the solution for makingthe ion exchange film. Therefore, product water produced by electricitygeneration can be guided through voids in the electrode layers to thediffusion layers and drained through voids in the diffusion layers well.

Preferably, in this invention, in the solutions for making the positiveand negative electrode layers, solvents having higher vaporizationtemperatures than the solvent used in the solution for making the ionexchange film are used. When solvents having higher vaporizationtemperatures than the solvent used in the solution for making the ionexchange film are used like this, the ion exchange film can be driedsurely, preferentially to the electrode layers. Therefore, permeation ofthe solution for making the ion exchange film into the electrode layerscan be much more efficiently suppressed.

In this invention, preferably, the above-mentioned first of theelectrode layers is divided into a first layer on the side away from theion exchange film and a second layer on the side in contact with the ionexchange film, and the porosity of the second layer is set lower thanthe porosity of the first layer. By making the porosity of the secondlayer low like this it is possible to suppress permeation of thesolution for making the ion exchange film into the second layer and itis possible to prevent the voids in the electrode layers beingdiminished by the solution for making the ion exchange film.

The above-mentioned porosity of the second layer is preferably 70 to75%. When the porosity of the second layer is less than 70%, theporosity is too low and there is a risk of the solution for making theion exchange film not permeating into the second layer in a suitableamount. In this case, it is difficult for the intimacy between the ionexchange film and the second layer to be kept good, and there is a riskof not securing the required effective area for reaction. Because ofthis, there is a risk of the activation overvoltage becoming high and itnot being possible for a current to be generated efficiently. To avoidthis, the porosity of the second layer is set to at least 70% to keepthe intimacy between the ion exchange film and the second layer good.

Here, “activation overvoltage” refers to a voltage drop which appears tomake up the activation energy necessary for the reactions at theelectrodes. That is, the activation overvoltage being high means theamount of the voltage drop being large. When on the other hand theporosity of the second layer exceeds 75%, there is a risk of thesolution for making the ion exchange film permeating the second layerexcessively due to the porosity being too high. In this case, the poresin the first electrode layer are diminished by the solution for makingthe ion exchange film, and the product water produced by electricitygeneration cannot be drained well through the pores in the firstelectrode layer. Consequently, the optimal supply of the reaction gaseshydrogen and oxygen is impeded, the density overvoltage becomes high,and it becomes difficult for the electricity generating performance ofthe fuel cell to be kept good. To avoid this, the porosity of the secondlayer is set to below 75% so that product water can be drained well.

Also, the porosity of the first layer is preferably 76 to 85%. When theporosity of the first layer is made less than 76%, the porosity is toolow and it is difficult for product water to be efficiently drained.Consequently, the optimal supply of the reaction gases hydrogen andoxygen is impeded, the density overvoltage becomes high, and it becomesdifficult for the electricity generating performance of the fuel cell tobe kept good. To avoid this, the porosity of the first layer is set toat least 76% so that product water can be drained well.

When on the other hand the porosity of the first layer exceeds 85%,there is a risk of the retention of product water falling due to theporosity being too high and of the first layer consequently drying andthe conduction of ions being hindered. Consequently, there is a risk ofresistance overvoltage becoming high and it not being possible forcurrent to be generated efficiently. To avoid this, the porosity of thefirst layer is set to below 85% to suppress resistance overvoltage andmake it possible for current to be generated efficiently.

Here, “resistance overvoltage” refers to a voltage drop arising inproportion to the electrical resistances inside the electrodes. That is,the resistance overvoltage being high means the amount of the voltagedrop being large.

In the method of this invention, to make the porosity of the secondlayer lower than the porosity of the first layer, preferably, thesolution for making the second layer is applied with a higheratomization energy than the solution for making the first layer. In thiscase, the density of the second layer becomes higher than the density ofthe first layer, and the porosity of the second layer becomes smallerthan the porosity of the first layer.

Also, in this invention, to make the porosity of the second layer lowerthan the porosity of the first layer, alternatively, the density of thesecond layer may be made higher than the density of the first layer bythe size of electrode particles included in the solution for making thesecond layer being made smaller than the size of electrode particlesincluded in the solution for making the first layer.

In the method of this invention, preferably, a step of forming a firstelectrode side diffusion layer, before the step of forming the firstelectrode layer, is included, the first electrode layer then beingformed while the first electrode side diffusion layer is not yet dry,and also a step of forming a second electrode side diffusion layer,after the second electrode layer is formed, is included, the secondelectrode side diffusion layer being formed while the second electrodelayer is not yet dry.

Preferably, the first electrode side diffusion layer is made up of apositive electrode side carbon paper and a positive electrode sidebinder layer, and the second electrode side diffusion layer is made upof a negative electrode side carbon paper and a negative electrode sidebinder layer.

The solution for making this positive electrode side binder layer,preferably, includes water as a solvent and includes a low-melting-pointresin having water repellency and a melting point of not greater than150° C.

Generally, so that product water can be drained efficiently to outsidethe fuel cell, a solution including a water repellent resin(polytetrafluoroethylene, for example trade name “Teflon” (a registeredtrade mark)) is applied to the positive electrode side carbon paper tomake the positive electrode side carbon paper water repellent. However,because the melting point of polytetrafluoroethylene is high, at 350°C., compared to the positive and negative electrode layers and the ionexchange film, it is necessary to fire individually only thepolytetrafluoroethylene, separately from the positive and negativeelectrode layers and the ion exchange film, and to dry the positive andnegative electrode layers and the ion exchange film after thepolytetrafluoroethylene is fired. Because of this, in the manufacture ofa fuel cell electrode, two drying steps, a drying step of firing thepolytetrafluoro-ethylene and a drying step of drying the positive andnegative electrode layers and the ion exchange film, are needed, andthis electrode manufacture takes time and labor.

To avoid this, to reduce the number of drying steps, as mentioned above,in this invention, in place of the above-mentionedpolytetrafluoroethylene as the water repellent resin, alow-melting-point resin whose melting point is below 150° C. is used.That is, when the melting point of the water repellent resin exceeds150° C., there is a risk of it not being possible to fire the waterrepellent resin together with the positive and negative electrode layersand the ion exchange film because its melting point temperature is toohigh. Because of this, the water repellent resin is made a resin with alow melting point below 150° C., whereby it is made possible to fire thewater repellent resin as well at the time of the drying of the positiveand negative electrode layers and the ion exchange film.

When it is possible to fire the water repellent resin as well at thetime of the drying of the positive and negative electrode layers and theion exchange film like this, the solution for making the positiveelectrode layer can be applied to the positive electrode side diffusionlayer before the water repellent resin (i.e. the positive electrode sidediffusion layer) has dried, and optimal mixing can be obtained at theinterface of the positive electrode side diffusion layer and thepositive electrode layer.

Here, because the surface of the positive electrode side carbon paper isan irregular surface, it is difficult to apply the solution of thepositive electrode side binder layer (and in particular the waterrepellent resin) to depressions in the positive electrode side carbonpaper.

Because of this, in this invention, as mentioned above, water isincluded as a solvent in the solution for making the positive electrodeside binder layer. Because water has excellent dispersing power, byusing water as the solvent it is possible to mix the low-melting-pointresin and the carbon well with the solvent. Therefore, the solution formaking the positive electrode side binder layer can be applied in sprayform by a sprayer or an ink jet or the like, and the solution for makingthe positive electrode side binder layer can be applied well even to thedepressions in the positive electrode side carbon paper.

A suitable example of the low-melting-point resin is vinylidenefluoride/tetrafluoroethylene/hexafluoropropylene copolymer. Thisvinylidene fluoride/tetrafluoroethylene/hexafluoropropylene copolymerhas the property of dispersing in water as a solvent, and can be used towork this invention well with a drying temperature of 150° C. That is,after the water serving as the solvent has evaporated, the vinylidenefluoride/tetrafluoroethylene/hexafluoropropylene copolymer which hadbeen dispersed in the water reaches its melting point and melts andexhibits a water repellent effect.

In the invention, the solution for making the positive electrode sidebinder layer includes an organic solvent. Because an organic solvent hasexcellent dissolving power, the water repellent resin can be dissolvedwell in the solvent. The carbon is dispersed or mixed in the solvent.Here, because the drying temperature of the organic solvent is likely tobe about 70 to 80° C., in the drying of the positive and negativeelectrode layers and the ion exchange film, the organic solvent can beevaporated with the water repellent resin being left behind, and thewater repellent resin can be fired together with the positive andnegative electrode layers and the ion exchange film. Because the waterrepellent resin can be fired as well at the time of the drying of thepositive and negative electrode layers and the ion exchange film likethis, the solution of the positive electrode layer can be applied to thepositive electrode side diffusion layer before the water repellent resin(i.e. the positive electrode side diffusion layer) has dried, andoptimal mixing can be obtained at the interface of the positiveelectrode side diffusion layer and the positive electrode layer.

As mentioned above, an organic solvent has excellent dissolvingcapacity, and by using an organic solvent it is possible to dissolve thewater repellent resin in the solvent well. In this way, the solution formaking the positive electrode side binder layer can be sprayed andapplied with a sprayer or an ink jet, and the solution for making thepositive electrode side binder layer can be applied well even to thedepressions in the surface of the positive electrode side carbon paper.

Also, the solution for making the positive electrode side binder layerof this invention includes a resin which is soluble in an organicsolvent and is water repellent. As this water repellent resin soluble inan organic solvent, suitable examples include vinylidenefluoride/tetrafluoroethylene/hexafluoropropylene copolymers,polyvinylidene fluoride, fluoro-olefin/hydrocarbon-olefin copolymers,fluoro-acrylate copolymers, and fluoro-epoxy compounds.

Also, in this invention, a first of positive and negative electrodelayers is formed on a binder layer of a first of a positive electrodeside diffusion layer and a negative electrode side diffusion layer, anion exchange film is formed on this first electrode layer, the secondelectrode layer is formed on this ion exchange film, a second binderlayer is formed on this second electrode layer, a second carbon paper isplaced on this second binder layer, and to make intimate the contactbetween the second binder layer and the second carbon paper, an adhesiveresin with excellent adhesion is included in a solution for making thesecond binder layer. As the adhesive resin, preferably, an ion exchangeresin is used.

This invention further includes a step of, after the first diffusionlayer is formed, flattening the upper face of the first diffusion layerby pressing the upper face of the first diffusion layer before the firstdiffusion layer has dried. By flattening the upper face of the firstdiffusion layer like this it is possible to apply the negative electrodelayer to the diffusion layer flatly, and also the ion exchange film canbe applied flatly to the negative electrode layer. Thus, by forming theion exchange film flatly, it is possible to prevent the positiveelectrode layer and the negative electrode layer applied to the ionexchange film from short-circuiting.

This first diffusion layer is preferably made by applying a binder to asheet consisting of carbon paper, because the binder can be applied tothe depressions in the carbon paper. In this way the binder can beapplied to the whole area of the carbon paper to obtain a waterrepellent effect, and product water produced by the reaction of hydrogenmolecules with oxygen molecules can be drained well.

The invention also provides an ion exchange film forming method forforming an ion exchange film for use in a fuel cell by forming a slurryon a first electrode of positive and negative electrodes of the fuelcell, including: a step of placing the first electrode on a bed andgiving this first electrode a plus charge; a step of, with a slurry formaking the ion exchange film given a minus charge, spraying the slurryfrom a slurry nozzle and moving the slurry nozzle over the firstelectrode to apply the sprayed slurry to the electrode; and a step ofdrying this applied slurry.

In this way, in this invention, by a positive or negative electrodebeing given a plus charge and a slurry for making an ion exchange filmbeing sprayed from a slurry nozzle with a minus charge, applicationnonuniformity of the slurry can be prevented. By this means it ispossible to apply the slurry to the negative electrode well, and the ionexchange film can be formed flat.

When the first electrode is polygonal, preferably, at narrow parts ofthe first electrode the slurry nozzle is brought close to the electrode,and at wide parts of the electrode the slurry nozzle is moved away fromthe electrode. By the slurry nozzle being brought close to narrow partsof the electrode, the width of the slurry sprayed from the slurry nozzlecan be narrowed, so that slurry does not land outside of the narrowparts of the electrode. And by moving the slurry nozzle away from theelectrode at wide parts of the electrode, the width of the slurrysprayed from the slurry nozzle can be widened, so that the wide parts ofthe electrode are coated with slurry. By adjusting the height of theslurry nozzle in accordance with the width of the electrode like this itis possible to prevent slurry projecting from the electrode and preventslurry being applied to excess areas.

The invention also provides an ion exchange film forming method forforming an ion exchange film for use in a fuel cell by forming a slurryon a first electrode of polygonal positive and negative electrodes ofthe fuel cell, having: a step of placing the first electrode on a bed; astep of disposing a plurality of slurry nozzles for spraying a slurryfor making the ion exchange film in the form of a zigzag; a step ofapplying the sprayed slurry to the surface of the first electrode whilemoving the slurry nozzles horizontally over the surface of the firstelectrode; and a step of drying the applied slurry.

Thus with this forming method, a plurality of slurry nozzles are used,and in the application of the slurry, when some of the slurry nozzlesare off the electrode, slurry is not sprayed from these slurry nozzles.By this means it is possible to avoid applying slurry to areas off theelectrode.

Also, because the ion exchange film is formed by spraying slurry formaking the ion exchange film from multiple slurry nozzles, the amountsof slurry sprayed from the slurry nozzles can be adjusted individually.By this means it is possible to form the surface of the ion exchangefilm flat relatively simply, without unnecessarily raising the sprayingaccuracy of the slurry nozzles.

Also, to prevent turbulence arising in the peripheral parts of thesprayed slurry, the slurry nozzles are disposed in the form of a zigzagand disposed so that peripheral parts of slurry sprayed from adjacentnozzles overlap. However, when the multiple slurry nozzles move over thesurface of the first electrode, to make up the amounts applied to theperipheral parts the peripheral parts of the applied slurry are made tooverlap, so that the amounts applied to the peripheral parts aresupplemented. As a result, the amounts applied to the peripheral partsand the amounts applied to the central part become equal, and a flat ionexchange film is obtained.

The forming method of this invention preferably includes a step of,after the first electrode is placed on the bed, disposing a guide framemember along the periphery of the first electrode, so that the regionover which the slurry is applied is regulated with this guide framemember. When the region over which the slurry is applied is limited witha guide frame member like this, the slurry can be formed easily to therequired shape, and without time and labor the edges of the ion exchangefilm can be formed well.

Also, the invention provides an ion exchange film forming method forforming an ion exchange film for use in a fuel cell by forming a slurryon a first electrode of positive and negative electrodes of the fuelcell, made up of: a step of placing the first electrode on a bed; a stepof disposing an outer side regulating wall member along the periphery ofthis first electrode and surrounding the first electrode with this outerside regulating wall member; and a step of spraying a resin solutionincluding a gas from a spraying device disposed above this firstelectrode and moving this spraying device over the surface of the firstelectrode to apply the resin solution to the first electrode.

In this way, in this forming method, by a spraying device being disposedabove the electrode and a resin solution being sprayed through thisspraying device to apply the resin solution to the electrode, a shearforce can be prevented from arising at the electrode. Also, by sprayinga resin solution including a gas, it is possible to keep the spraypressure down. By this means, when the resin solution is applied to theelectrode, the surface of the electrode is prevented from shifting.

Additionally, by a resin solution including a gas being sprayed, whenthe resin solution is sprayed at the edge of the electrode, theatomization pressure arising at the edge of the electrode, that is, theshear force, can be kept small. By this means, the shear force arisingat the electrode can be kept small, and a surface layer part of theelectrode shifting can be prevented.

Also, by the electrode being surrounded with an outer side regulatingwall member, when the resin solution is applied to the electrodesurface, the resin solution can be formed along the outer sideregulating wall member. As a result, the edge of the ion exchange filmcan be formed well.

The invention also provides a fuel cell electrode, made up of: a firstelectrode layer, formed by applying a solution for making a firstelectrode of positive and negative electrodes of a fuel cell to a sheet;an ion exchange film, formed by applying a solution for making an ionexchange film to the first electrode layer before the first electrodelayer has dried; and a second electrode layer, formed by applying asolution for making the second electrode to the ion exchange film beforethe ion exchange film has dried, wherein the first electrode layer ismade up of a first layer on the side away from the ion exchange film anda second layer on the side in contact with the ion exchange film, andthe porosity of the second layer is lower than the porosity of the firstlayer.

Preferably, the porosity of the second layer is 70 to 75%, and theporosity of the first layer is 76 to 85%.

Also, in the invention, the porosity of the second layer may be madelower than the porosity of the first layer by the size of electrodeparticles included in a solution for making the second layer being madesmaller than the size of electrode particles included in a solution formaking the first layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view showing a fuel cell according toa first embodiment of the invention;

FIG. 2 is a view showing the cross-sectional structure of a fuel cellelectrode shown in FIG. 1;

FIG. 3A through FIG. 3F are views illustrating steps of a first methodfor manufacturing the fuel cell electrode of the first embodiment shownin FIG. 1;

FIG. 4A through FIG. 4E are views illustrating steps of a second methodfor manufacturing the fuel cell electrode of the first embodiment shownin FIG. 1;

FIG. 5 is a view showing an example of thermal drying in a method formanufacturing the fuel cell electrode of the first embodiment;

FIG. 6A and FIG. 6B are graphs illustrating a relationship between voidvolume and density overvoltage in the fuel cell electrode of the firstembodiment;

FIG. 7 is a view showing the cross-sectional structure of a fuel cellelectrode according to a second embodiment of the invention;

FIG. 8A through FIG. 8H are views illustrating steps of a method formanufacturing the fuel cell electrode of the second embodiment shown inFIG. 7;

FIG. 9 is a view showing the cross-sectional structure of a fuel cellelectrode according to a third embodiment of the invention;

FIG. 10A through FIG. 10I are views illustrating steps of a method formanufacturing the fuel cell electrode of the third embodiment shown inFIG. 9;

FIG. 11 is a view showing the cross-sectional structure of a fuel cellelectrode according to a fourth embodiment of the invention;

FIG. 12A through FIG. 12G are views illustrating steps of a method formanufacturing the fuel cell electrode of the fourth embodiment shown inFIG. 11;

FIG. 13 is a view showing the cross-sectional structure of a fuel cellelectrode according to a fifth embodiment of the invention;

FIG. 14A, FIG. 14B and FIG. 14C are views illustrating some steps of amethod for manufacturing the fuel cell electrode of the fifth embodimentshown in FIG. 13;

FIG. 15 is a view showing the cross-sectional structure of a fuel cellelectrode according to a sixth embodiment of the invention;

FIG. 16A through FIG. 16H are views illustrating steps of a first methodfor manufacturing the fuel cell electrode of the sixth embodiment shownin FIG. 15;

FIG. 17A and FIG. 17B are views illustrating some steps of a secondmethod for manufacturing the fuel cell electrode of the sixth embodimentshown in FIG. 15;

FIG. 18 is an exploded perspective view of a fuel cell having a fuelcell electrode according to a seventh embodiment;

FIG. 19 is sectional view of an ion exchange film for the fuel cellshown in FIG. 18;

FIG. 20 is a perspective view of a forming apparatus for carrying out afirst method for forming the ion exchange film for a fuel cell shown inFIG. 19;

FIG. 21 is a sectional view of the forming apparatus shown in FIG. 20;

FIG. 22A through FIG. 22J are views illustrating steps of the firstmethod for forming an ion exchange film for a fuel cell according to theinvention;

FIG. 23 is a sectional view of a forming apparatus for carrying out asecond method for forming the ion exchange film for a fuel cell shown inFIG. 19;

FIG. 24 is a perspective view of a forming apparatus for carrying out athird method for forming the ion exchange film for a fuel cell shown inFIG. 19;

FIG. 25 is a plan view of the forming apparatus shown in FIG. 24;

FIG. 26 is a sectional view of the forming apparatus shown in FIG. 24;

FIG. 27A through FIG. 27J are views showing steps of the third methodfor forming the ion exchange film for a fuel cell shown in FIG. 19;

FIG. 28A and FIG. 28B are views comparing characteristics of the thirdmethod for forming the ion exchange film for a fuel cell of theinvention with a comparison example;

FIG. 29 is a sectional view of an ion exchange film forming apparatusfor carrying out a fourth method of forming an ion exchange film for afuel cell;

FIG. 30 is an exploded perspective view of a fuel cell having anelectrode of an eighth embodiment of the invention;

FIG. 31 is a sectional view showing an ion exchange film for the fuelcell shown in FIG. 30;

FIG. 32A through FIG. 32G are views illustrating steps of a method forforming the ion exchange film for a fuel cell shown in FIG. 31;

FIG. 33 is a schematic view of a fuel cell of related art;

FIG. 34 is a view showing the electrode structure of the fuel cell shownin FIG. 33;

FIG. 35A and FIG. 35B are views illustrating a method for forming an ionexchange film of the fuel cell electrode of related art shown in FIG.33;

FIG. 36A and FIG. 36B are views illustrating another method for formingan ion exchange film of a fuel cell electrode of related art.

BEST MODE FOR CARRYING OUT THE INVENTION

A number of preferred embodiments of the invention will be describedbelow on the basis of the accompanying drawings.

As shown in FIG. 1, a fuel cell unit 10 is made up of a plurality of (inthe example shown in the figure, two) fuel cells 11, 11. A fuel cell 11according to a first embodiment shown in FIG. 1 has a negative electrodeside flow channel plate 31 disposed on the outer side of a negativeelectrode side diffusion layer (sheet) 13 of a fuel cell electrode(hereinafter called simply an electrode) 12, and a positive electrodeside flow channel plate 34 disposed on the outer side of a positiveelectrode side diffusion layer 16 of the electrode 12.

By the negative electrode side flow channel plate 31 being stackedagainst the negative electrode side diffusion layer 13, multiple flowchannels 31a formed in the negative electrode side flow channel plate 31are covered by the negative electrode side diffusion layer 13, andmultiple horizontal hydrogen gas flow passages 32 are thereby formed. Bythe positive electrode side flow channel plate 34 being stacked againstthe positive electrode side diffusion layer 16, multiple flow channels34 a formed in the positive electrode side flow channel plate 34 arecovered by the positive electrode side diffusion layer 16, and multiplevertical oxygen gas flow passages 35 are thereby formed. The hydrogengas flow passages 32 and the oxygen gas flow passages 35 are disposed sothat they are at right angles.

The electrode 12 has a negative electrode layer 19 serving as oneelectrode layer and a positive electrode layer 20 serving as the otherelectrode layer on binder layers respectively on the inner sides of thenegative electrode side diffusion layer 13 and the positive electrodeside diffusion layer 16, and has an ion exchange film 21 interposedbetween the negative electrode layer 19 and the positive electrode layer20.

By multiple fuel cells 11 constructed like this being stacked withseparators 36 therebetween, the fuel cell unit lo is constructed.

With this fuel cell unit 10, by hydrogen gas being supplied to thehydrogen gas flow passages 32, hydrogen molecules (H₂) are adsorbed ontoa catalyst included in the negative electrode layer 19, and by oxygengas being supplied to the oxygen gas flow passages 35, oxygen molecules(O₂) are adsorbed onto a catalyst included in the positive electrodelayer 20. By this means, electrons (e⁻) can be made to flow as shownwith arrows, so that a current is generated. In the generation of thecurrent, product water (H₂O) is produced from the hydrogen molecules(H₂) and the oxygen molecules (O₂).

FIG. 2 shows the cross-sectional structure of the electrode 12 of thefirst embodiment shown in FIG. 1.

The electrode 12 of the first embodiment has the negative electrodelayer 19 and the positive electrode layer 20 respectively on the innersides of the negative electrode side diffusion layer 13 and the positiveelectrode side diffusion layer 16, and has an ion exchange film 21between the negative electrode layer 19 and the positive electrode layer20.

The negative electrode side diffusion layer 13 is a sheet made up of anegative electrode side carbon paper 14 and a negative electrode sidebinder layer 15.

The positive electrode side diffusion layer 16 is a sheet made up of apositive electrode side carbon paper 17 and a positive electrode sidebinder layer 18.

The binder of the negative electrode side binder layer 15 is acarbon-fluoro resin and is excellent in hydrophilicity. The binder ofthe positive electrode side binder layer 18 is a carbon polymerexcellent in water repellency. As the carbon polymer, one made byintroducing sulfonic acid into a polytetrafluoroethylene structure issuitable.

The negative electrode layer 19 is made by mixing a solution for makinga negative electrode with a catalyst 22 and hardening the solution bydrying it after it is applied. The catalyst 22 of the negative electrodelayer 19 is one made by attaching a platinum-ruthenium alloy 24 as acatalyst to the surface of carbon 23, and hydrogen molecules (H₂) areadsorbed onto the platinum-ruthenium alloy 24.

The positive electrode layer 20 is made by mixing a solution for makinga positive electrode with a catalyst 25 and hardening the solution bydrying it after it is applied. The catalyst 25 of the positive electrodelayer 20 is one made by attaching platinum 27 as a catalyst to thesurface of carbon 26, and oxygen molecules (O₂) are adsorbed onto theplatinum 27.

The ion exchange film 21 is formed by applying a solution between thenegative electrode layer 19 and the positive electrode layer 20 andhardening it together with the negative electrode layer 19 and thepositive electrode layer 20 by drying it together with the negativeelectrode solution and the positive electrode solution.

Next, a method of manufacturing the electrode 12 of the first embodimentof the invention will be described, on the basis of FIG. 3A through FIG.3F.

In FIG. 3A, a sheet-form negative electrode side diffusion layer 13 isprepared by forming a binder layer 15 on a carbon paper 14.

In FIG. 3B, a solution for making a negative electrode is applied to thebinder layer 15 to form the negative electrode layer 19.

In FIG. 3C, before the negative electrode layer 19 has dried, a solutionfor making the ion exchange film 21 is applied to the negative electrodelayer 19 to form the ion exchange film 21.

In FIG. 3D, before the ion exchange film 21 has dried, a solution formaking the positive electrode layer 20 is applied to the ion exchangefilm 21 to form the positive electrode layer 20.

In FIG. 3E, before the positive electrode layer 20 has dried, thepositive electrode side diffusion layer 16, made up of the positiveelectrode side carbon paper 17 and the positive electrode side binderlayer 18, is formed on the positive electrode layer 20.

Next, before the negative electrode layer 19, the ion exchange film 21and the positive electrode layer 20 have dried, without a load beingapplied to the layers 19 and 20 and the film 21, the layers 19 and 20and the film 21 are dried together.

In FIG. 3F, by the negative electrode layer 19, the ion exchange film 21and the positive electrode layer 20 being hardened, the negativeelectrode layer 19, the ion exchange film 21 and the positive electrodelayer 20 are laminated in a hardened state.

Thus, with the manufacturing method of the electrode 12 of the firstembodiment, by employing a solution for the ion exchange film 21 andapplying the solution for making the negative electrode layer 19, thesolution for making the ion exchange film 21 and the solution for makingthe positive electrode layer 20 in an undried state, the solutionsadjacent at the respective interfaces can be mixed well. By this meansit is possible to prevent the occurrence of areas of defective intimacyat the interface between the binder layer 15 and the negative electrodelayer 19, the interface between the negative electrode layer 19 and theion exchange film 21, the interface between the ion exchange film 21 andthe positive electrode layer 20, and the interface between the positiveelectrode layer 20 and the positive electrode side binder layer 18, andthe reaction efficiency of the electrode 12 can be kept good.

Also, the respective solutions are applied with the negative electrodelayer 19, the ion exchange film 21 and the positive electrode layer 20in an undried state, and the respective solutions are dried afterapplication without any load being applied. As a result, in thehardening of the ion exchange film 21, it is not necessary for a load tobe applied to the ion exchange film 21, and consequently the performanceof the ion exchange film 21 can be prevented from dropping due to theinfluence of a load.

Also, because as a result of the ion exchange film 21 being made asolution the ion exchange film 21 can be handled in the form of asolution, it is not necessary for the thickness of the ion exchange film21 to be regulated from the handling point of view. Consequently, theion exchange film 21 can be made thin, and the electrode 12 can be madethin.

Next, a variation of the method of manufacturing a fuel cell electrodeof the first embodiment will be described, on the basis of FIG. 4Athrough FIG. 4E. Parts the same as parts of the electrode of the firstembodiment have been given the same reference numbers and a descriptionthereof will be omitted.

In FIG. 4A, a sheet-form negative electrode side diffusion layer 13 islaid. That is, a carbon paper 14 of a negative electrode side diffusionlayer 13 is set, and then a solution for making a binder layer 15 isapplied to this carbon paper 14.

In FIG. 4B, before the binder layer 15 has dried, a solution for makinga negative electrode layer 19 is sprayed in atomized form from a spraynozzle 42 while a sprayer 41 is moved across the upper face of thebinder layer 15 as shown with an arrow, whereby the solution for makingthe negative electrode layer 19 is applied to the binder layer 15 andthe negative electrode layer 19 is formed.

In the solution for making this negative electrode layer 19, a solventhaving a higher vaporization temperature than the solvent used in thesolution for making the ion exchange film 21 shown in FIG. 2 is used.

As an example here, an alcohol solvent is used in the solution formaking the ion exchange film 21 to be applied to the negative electrodelayer 19, and in the solution of the negative electrode layer 19ethylene glycol or N-methyl-2-pyrolidone (NMP) with a highervaporization temperature than the alcohol solvent is used as thesolvent. The reason for using in the solution of the negative electrodelayer 19 a solvent having a higher vaporization temperature than thesolvent used in the solution for making the ion exchange film 21 will bediscussed later.

In FIG. 4C, before the negative electrode layer 19 has dried, while acoater 45 is moved across the upper face of the negative electrode layer19 as shown by the arrow, the solution for making the ion exchange film21 is applied to the negative electrode layer 19 to form the ionexchange film 21. Specifically, a blade 45 a of the coater 45 isdisposed a predetermined spacing away from the upper face of thenegative electrode layer 19 and parallel with the upper face, and whilethis blade 45 a is moved across the upper face of the negative electrodelayer 19 as shown by the arrow the solution for making the ion exchangefilm 21 is leveled to a fixed thickness to form the ion exchange film21.

By employing a solution for the ion exchange film 21 and applying thesolution for making the ion exchange film 21 to the negative electrodelayer 19 before the negative electrode layer 19 has dried, the solutionsat the interface of the negative electrode layer 19 and the ion exchangefilm 21 can be mixed effectively.

As a result of the solution for making the ion exchange film 21 beingapplied to the negative electrode layer 19, the solution for making theion exchange film 21 flows downward under the influence of gravity asshown by the arrow and permeates the negative electrode layer 19. Thereis a risk of the voids of the negative electrode layer 19 beingdiminished by this, but even if the voids of the negative electrodelayer 19 diminish somewhat, there is no effect on the performance of thefuel cell.

In FIG. 4D, before the ion exchange film 21 has dried, by a solution formaking the positive electrode layer 20 being sprayed in an atomizedstate from a spray nozzle 44 as a sprayer 43 is moved across the upperface of the ion exchange film 21 as shown with an arrow, the solutionfor making the positive electrode layer 20 is applied to the ionexchange film 21 to form the positive electrode layer 20.

The reason for using the sprayer 43 to apply the solution for making thepositive electrode layer 20 to the upper face of the ion exchange film21 will be discussed later.

In the solution of the positive electrode layer 20, as in the solutionof the negative electrode layer 19, a solvent having a highervaporization temperature than the alcohol solvent used in the solutionfor making the ion exchange film 21 is used. As an example, in thesolution of the positive electrode layer 20 ethylene glycol orN-methyl-2-pyrolidone (NMP) with a higher vaporization temperature thanthe alcohol solvent is used as the solvent. The reason for using in thesolution of the positive electrode layer 20 a solvent having a highervaporization temperature than the solvent used in the solution formaking the ion exchange film 21 will be discussed later.

In FIG. 4E, before the positive electrode layer 20 has dried, a solutionfor making the binder layer 18 of the positive electrode side diffusionlayer 16 (see FIG. 2) is applied to the positive electrode layer 20 toform the binder layer 18.

Next, in the same way as in FIG. 3E, by a positive electrode side carbonpaper 17 being placed on the binder layer 18, a sheet-form positiveelectrode side diffusion layer 16 is formed with the binder layer 18 andthe carbon paper 17. After that, before the binder layer 15, thenegative electrode layer 19, the ion exchange film 21, the positiveelectrode layer 20 and the binder layer 18 have dried, without a loadbeing applied to the layers 15, 19, 20 and 18 and the film 21, thelayers 15, 19, 20 and 18 and the film 21 are dried together.

Finally, in the same way as in FIG. 3F, by the binder layer 15, thenegative electrode layer 19, the ion exchange film 21, the positiveelectrode layer 20 and the binder layer 18 being hardened, the binderlayer 15, the negative electrode layer 19, the ion exchange film 21, thepositive electrode layer 20 and the binder layer 18 are laminatedintegrally in a hardened state. A fuel cell electrode 12 is thusobtained.

In this way, in the first embodiment and its variation, the positiveelectrode layer 20 is provided on the ion exchange film 21. By thismeans, the solution for making the ion exchange film 21 can be preventedfrom permeating the positive electrode layer 20, and diminishing of thevoids of the positive electrode layer 20 by the solution for making theion exchange film 21 can be prevented. As a result, product waterproduced by electricity generation can be guided through the voids ofthe positive electrode layer 20 to the positive electrode side diffusionlayer 16 and drained well through the positive electrode side diffusionlayer 16, and consequently the density overvoltage arising in the fuelcell can be kept low.

Also, with the manufacturing method of the variation, in the forming ofthe positive electrode layer 20, by the solution for making the positiveelectrode layer 20 being applied by spraying, it is applied withoutexcess application pressure being exerted on the ion exchange film 21 orthe positive electrode layer 20, that is, the solution for making thepositive electrode 20 can be applied with a minimal applicationpressure. That is, by applying the solution for making the positiveelectrode 20 without exerting excess application pressure on the ionexchange film 21 or the positive electrode layer 20, it is possible toprevent the solution for making the ion exchange film 21 from permeatingthe positive electrode layer 20. Therefore, the voids of the positiveelectrode layer 20 are prevented from being diminished by the solutionfor making the ion exchange film 21,. and the voids of the positiveelectrode layer 20 can be secured much better. By this means it ispossible to guide product water produced by electricity generation fromthe positive electrode layer 20 to the positive electrode diffusionlayer 16 and drain it through voids in the positive electrode sidediffusion layer 16 much better, and density overvoltage arising in thefuel cell can be kept low.

Although in the variation the solution for making the positive electrodelayer 20 was applied to the ion exchange film 21 using a sprayer 43, theapplication of the solution for making the positive electrode layer 20is not limited to the sprayer 43, and it is also possible to employ theink jet method. In short, any method by which the solution for makingthe positive electrode layer 20 can be applied in spray form may beused.

Here, a sprayer applies the solution in the form of a spray, and an inkjet applies the solution in shots. With a sprayer the spray scope can bemade relatively large to shorten the application time, but a maskingprocess is necessary to obtain unsprayed parts. Generally, recoveringsolution landing on masked parts is difficult.

On the other hand, with an ink jet, because it is possible to focus theapplication scope exactly, there is no need for the non-applicationareas to be masked, and the solution can be used efficiently. However,because the application scope is narrow, compared to a sprayer theapplication speed is poorer.

Also, although in the variation an example was described wherein thesolution for making the negative electrode layer 19 was applied to thebinder layer 15 using a sprayer 41, the solution for making the negativeelectrode layer 19 can also be applied by other applying means.

Also, whereas in this variation an example was described wherein thesolution for making the ion exchange film 21 was applied to the negativeelectrode layer 19 using a coater 45, the solution for making the ionexchange film 21 can also be applied by other applying means.

Additionally, with the manufacturing method of the fuel cell electrode12, the solution for making the ion exchange film 21 can be preventedfrom permeating the negative electrode layer 19 and the positiveelectrode layer 20 and blocking the voids of the negative electrodelayer 19 and the positive electrode layer 20. Because consequentlyproduct water produced by the electricity generation of the fuel cellcan be guided through the voids in the negative and positive electrodelayers 19, 20 (and particularly the positive electrode layer 20) to thepositive electrode side diffusion layer 16 (the carbon paper 17 and thebinder layer 18) and drained well to outside through the voids in thepositive electrode side diffusion layer 16, the density overvoltagearising in the fuel cell can be kept low.

Also, by solvents with a higher vaporization temperature than thesolvent used in the solution for making the ion exchange film 21 beingused in the solution for the negative electrode layer 19 and thesolution for the positive electrode layer 20, the ion exchange film 21can be dried surely, preferentially to the negative electrode layer 19and the positive electrode layer 20. Therefore, permeation of thesolution for making the ion exchange film 21 into the negative electrodelayer 19 and the positive electrode layer 20 can be much moreeffectively suppressed, and the solution for making the ion exchangefilm 21 can be prevented from permeating the negative electrode layer 19and the positive electrode layer 20 and blocking the voids of thenegative electrode layer 19 and the positive electrode layer 20.

Although in the first embodiment and the variation thereof exampleswhere described wherein, in the manufacture of the fuel cell electrode12, the negative electrode layer 19 was disposed below and the positiveelectrode layer 20 was disposed above, the invention is not limited tothis, and alternatively the positive electrode layer 20 can be disposedbelow and the negative electrode layer 19 disposed above.

Next, an example wherein when the layers are dried they are dried bybeing heated artificially as shown in FIG. 5 will be described.

That is, before the negative electrode layer 19, the ion exchange film21 and the positive electrode layer 20 have dried, without a load beingapplied to the negative electrode layer 19, the ion exchange film 21 andthe positive electrode layer 20, they are dried together by being heatedfrom inside with a far infrared radiation drying apparatus(electromagnetic wave heating apparatus) 61. The far infrared radiationdrying apparatus 61 is a heating apparatus which uses far infraredradiation, meaning infrared radiation of long wavelength amongelectromagnetic waves in the infrared range, of a wavelength range ofabout 50 to 100 μm in wavelength.

Because this far infrared radiation drying apparatus 61 can heat theinside of a body efficiently, by drying the negative electrode layer 19,the ion exchange film 21 and the positive electrode layer 20 alltogether with the far infrared radiation drying apparatus 61, it ispossible to dry the whole of the ion exchange film 21 rapidly from itsinterior to its surfaces. By this means it is possible to suppresspermeation of the solution for making the ion exchange film 21 into thenegative electrode layer 19 and the positive electrode layer 20, andtherefore the solution for making the ion exchange film 21 can beprevented from blocking the voids of the negative electrode layer 19 andthe positive electrode layer 20.

FIG. 6A and FIG. 6B are graphs illustrating the relationship betweenvoid volume and density overvoltage in a fuel cell electrode accordingto the invention.

In the graphs, Test Example 1 is an example wherein an alcohol solventis used in the solution for making the ion exchange film 21 and ethyleneglycol or N-methyl-2-pyloridone (NMP) with a higher vaporizationtemperature than the alcohol solvent is used as the solvent in thesolution of the positive electrode layer 20. In Test Example 1, anordinary hot air drying apparatus was used for the drying of thenegative electrode layer 19, the ion exchange film 21 and the positiveelectrode layer 20. That is, in Test Example 1, a part of theimplementation described above (the ethylene glycol orN-methyl-2-pyloridone (NMP)) was employed.

In Test Example 2, the ethylene glycol or N-methyl-2-pyloridone (NMP)constituting the solvent of Test Example 1 was employed, and also a farinfrared radiation drying apparatus 61 was used for the drying of thenegative electrode layer 19, the ion exchange film 21 and the positiveelectrode layer 20.

In the comparison example, the ethylene glycol or N-methyl-2-pyloridone(NMP) constituting the solvent of Test Examples 1 and 2 was notemployed, and the far infrared radiation drying apparatus of TestExample 2 was not used either, and an ordinary hot air drying apparatuswas used.

In the graph of FIG. 6A, the comparison example has the smallest voidvolume of the positive electrode layer 20, in Test Example 1 a largervoid volume of the positive electrode layer 20 than in the comparisonexample has been obtained, and in Test Example 2 a larger void volume ofthe positive electrode layer 20 than in Test Example 1 has beenobtained. That is, Test Example 2 has the largest void rate of thepositive electrode layer 20.

In the graph of FIG. 6B, because the comparison example has the smallestvoid volume of the positive electrode layer 20, it has the largestdensity overvoltage of the fuel cell and the largest voltage drop of thefuel cell.

Because Test Example 1 has a larger void volume of the positiveelectrode layer 20, the density overvoltage of the fuel cell is smallerthan in the comparison example, and the voltage drop of the fuel cell isalso smaller than in the comparison example.

Because Test Example 2 has a larger void volume of the positiveelectrode layer 20 than Test Example 1, the density overvoltage of thefuel cell is smaller than in Test Example 1, and the voltage drop of thefuel cell is kept to a minimum.

Thus, it can be seen that, by using an alcohol solvent in the solutionfor making the ion exchange film 21 and using in the solution of thepositive electrode layer 20 ethylene glycol or N-methyl-2-pyloridone(NMP) with a higher vaporization temperature than the alcohol solvent,as in Test Example 1, it is possible to suppress the voltage drop of thefuel cell relatively well.

Also, it can be seen that by employing the ethylene glycol orN-methyl-2-pyloridone (NMP) constituting the solvent of Test Example 1and also drying the negative electrode layer 19, the ion exchange film21 and the positive electrode layer 20 with a far infrared radiationdrying apparatus 61, as in Test Example 2, it is possible to keep thevoltage drop of the fuel cell to a minimum with the most effectiveness.

Although in the first embodiment an example was described wherein thenegative electrode layer 19 was disposed below and the positiveelectrode layer 20 was disposed above, the same effects can also beobtained by disposing the negative electrode layer 19 above anddisposing the positive electrode layer 20 below.

And, in the embodiment using the far infrared radiation drying apparatus61, instead of the far infrared radiation drying apparatus 61, forexample a microwave drying apparatus can be used. A microwave dryingapparatus is a heating apparatus which uses microwaves in the wavelengthrange of about 1×10⁴ to 30×10⁴ μm in wavelength.

Also, there being no restriction to a far infrared radiation dryingapparatus 61 or microwaves, the same effects can be obtained by usingheating means using electromagnetic waves of wavelength 50 to 30×10⁴ μm.

In the example wherein the ion exchange film 21 is heated and dried withjust the far infrared radiation drying apparatus 61 (electromagneticwave drying apparatus), the far infrared radiation drying apparatus 61and a hot air drying apparatus can be used in combination.

Although in the first embodiment an example was described wherein analcohol solvent was used in the solution for making the ion exchangefilm 21 and ethylene glycol or N-methyl-2-pyloridone (NMP) with a highervaporization temperature than the alcohol solvent was used as thesolvent for the solutions of both the negative electrode layer 19 andthe positive electrode layer 20, there is no restriction to this, andthe same effects can also be obtained by using ethylene glycol orN-methyl-2-pyloridone (NMP) with a higher vaporization temperature thanthe alcohol solvent as the solvent in the solution of the positiveelectrode layer 20 only. The reason for this is that when the fuel cellis used to generate current, because the product water produced drainsto outside the fuel cell through the positive electrode side diffusionlayer (carbon paper), the product water can be drained to outside thefuel cell as long as voids in the positive electrode layer 20 aresecured.

Next, a fuel cell electrode of a second embodiment, wherein the positiveelectrode layer is made up of two layers, will be described, on thebasis of FIG. 7. Parts the same as parts shown in the first embodimenthave been given the same reference numbers.

The fuel cell electrode 62 of this embodiment has a negative electrodelayer 19 and a positive electrode layer 60 on the inner sides of anegative electrode side diffusion layer 13 and a positive electrode sidediffusion layer 16 respectively, and has an ion exchange film 21 betweenthe negative electrode layer 19 and the positive electrode layer 60.

The negative electrode side diffusion layer 13 is a sheet made up of anegative electrode side carbon paper 14 and a negative electrode sidebinder layer 15. The positive electrode side diffusion layer 16 is asheet made up of a positive electrode side carbon paper 17 and apositive electrode side binder layer 18.

The binder constituting the negative electrode side binder layer 15 is avery hydrophilic carbon fluoropolymer. The binder constituting thepositive electrode side binder layer 18 is a carbon polymer excellent inwater repellency. A carbon polymer made by introducing sulfonic acidinto a polytetrafluoroethylene matrix is suitable.

The negative electrode layer 19 is made by mixing a catalyst 22 with asolution for making a negative electrode and hardening the solution bydrying it after it is applied. The catalyst 22 of the negative electrodelayer 19 is one made by attaching a platinum-ruthenium alloy 24 as acatalyst to the surface of carbon 23, and hydrogen molecules (H₂) areadsorbed onto the platinum-ruthenium alloy 24.

The positive electrode layer 60 is divided into a first layer 60 a onthe side away from the ion exchange film 21 (i.e. the side in contactwith the positive electrode side diffusion layer 16) and a second layer60 b on the side in contact with the ion exchange film 21, and whenporosity is defined by the following equation (1), the second layer 60 bhas a lower porosity than the first layer 60 a.POROSITY=(1−BULK S. G./TRUE S. G.)×100   (1)Here, true specific gravity refers to the specific gravity of thematerial when it has no voids or pores inside it. Bulk specific gravityrefers to the specific gravity of the material including voids and poresassuming it has a uniform density distribution.

The first layer 60 a is made by mixing a catalyst 25 with a solution formaking the first layer 60 a and hardening the solution by drying itafter it is applied. The catalyst 25 of the first layer 60 a is one madeby attaching platinum 27 as a catalyst to the surface of carbon 26, andoxygen molecules (O₂) are adsorbed onto this platinum 27.

The second layer 60 b, like the first layer 60 a, is made by mixing acatalyst 25 with a solution for making the second layer 60 b andhardening the solution by drying it after it is applied. The catalyst 25of the second layer 60 b is one made by attaching platinum 27 as acatalyst to the surface of carbon 26, and oxygen molecules (O₂) areadsorbed onto this platinum 27.

In this second layer 60 b the catalyst 25 is disposed more denselycompared to the catalyst 25 in the first layer 60 a, to make theporosity of the second layer 60 b smaller than that of the first layer60 a. Specifically, the porosity of the second layer 60 b is 70 to 75%and the porosity of the first layer 60 a is 76 to 85%.

Here, the reasons for setting the porosity of the second layer 60 b to70 to 75% will be explained.

When the porosity of the second layer 60 b is less than 70%, there is arisk of the porosity being too low and the solution for making the ionexchange film 21 not permeating into the second layer 60 b in a suitableamount. In this case, it is difficult for the intimacy between the ionexchange film 21 and the second layer 60 b to be kept good. To avoidthis, the porosity of the second layer 60 b is set to at least 70% tokeep the intimacy between the ion exchange film 21 and the second layer60 b good.

When the porosity of the second layer 60 b exceeds 75%, there is a riskof the solution for making the ion exchange film 21 permeating thesecond layer 60 b excessively due to the porosity being too high. Inthis case, the pores in the first electrode layer 60 are diminished bythe solution for making the ion exchange film 21, and the product waterproduced by electricity generation cannot be drained well through thepores in the first electrode layer 60. To avoid this, the porosity ofthe second layer 60 b is set to below 75% so that product water can bedrained well.

Next, the reasons for setting the porosity of the first layer 60 a to 76to 85% will be explained.

When the porosity of the first layer 60 a is made less than 76%, theporosity is too low and it is difficult for product water to beefficiently drained. To avoid this, the porosity of the first layer 60 ais set to at least 76% so that product water can be drained well.

When the porosity of the first layer 60 a exceeds 85%, there is a riskof the retention of product water falling due to the porosity being toohigh and of the first layer 60 a consequently drying and the conductionof ions being hindered. Consequently, there is a risk of resistanceovervoltage becoming high and it not being possible for current to begenerated efficiently. To avoid this, the porosity of the first layer 60a is set to below 85% to suppress resistance overvoltage and make itpossible for current to be generated efficiently.

The ion exchange film 21 is formed by applying a solution between thepositive electrode layer 60 (specifically, the second layer 60 b) andthe negative electrode layer 19 and hardening it together with thenegative electrode layer 19 and the positive electrode layer 60 bydrying it together with the negative electrode layer 19 and the positiveelectrode layer 60.

Next, a method of manufacturing the fuel cell electrode 12 of the secondembodiment shown in FIG. 7 will be described, on the basis of FIG. 8Athrough FIG. 8H.

In FIG. 8A, the sheet-form positive electrode side diffusion layer 16 islaid. That is, the carbon paper 17 of the positive electrode sidediffusion layer 16 is set and then a solution for making the binderlayer 18 is applied to this carbon paper 17.

In FIG. 8B, before the binder layer 18 has dried, a sprayer 41 is movedover the binder layer 18 as shown by the arrow [1], and a solution forforming the first layer 60 a of the positive electrode layer 60 isapplied to the binder layer 18 through a spray nozzle 42. By this means,the first layer 60 a is formed on the binder layer 18.

Here, when porosity is defined with the above equation (1), the porosityof the first layer 60 a is made 76 to 85%.

Before the first layer 60 a has dried, the sprayer 41 is moved over thefirst layer 60 a as shown by the arrow [1] again and a solution formaking the second layer 60 b of the positive electrode layer 60 isapplied to the first layer 60 a through the spray nozzle 42. By thismeans, the second layer 60 b is formed on the first layer 60 a.

As the solution of the second layer 60 b, the same solution as thesolution of the first layer 60 a is used, and the spray pressure, thatis, atomization pressure (atomization energy), of the solution formaking the second layer 60 b is set higher than the spray pressure, thatis, atomization pressure (atomization energy), of the solution formaking the first layer 60 a. Specifically, when porosity is defined bythe above equation (1), the porosity of the second layer 60 b is made 70to 75%. As a result of the atomization pressure of the solution formaking the second layer 60 b being set high, the spraying speed of thesolution also rises.

By the solution for making the second layer 60 b being applied with ahigher atomization energy than the solution for making the first layer60 a like this, the density of the second layer 60 b can be made higherthan the density of the first layer 60 a and the porosity of the secondlayer 60 b can be made lower than the porosity of the first layer 60 a.

Although in the electrode manufacturing method of the second embodimentan example was described in which the solution for making the firstlayer 60 a and the solution for making the second layer 60 b were bothapplied in the form of a spray with the same sprayer 41, there is norestriction to this, and it is also possible to apply the solutionsusing respective different sprayers for the solution for making thefirst layer 60 a and the solution for making the second layer 60 b, andmaking the respective spray pressures (atomization pressures) different.

Also, as the means for setting the atomization energy of the solutionfor making the second layer 60 b higher than the atomization energy ofthe solution for making the first layer 60 a, instead of the atomizationpressure, alternatively the atomization energy can be raised by bringingthe spray nozzle 42 of the sprayer 41 closer to the application surface.

In FIG. 8C, by the atomization pressure of the solution for making thesecond layer 60 b being set higher than the atomization pressure of thesolution for making the first layer 60 a, the catalyst 25 of the secondlayer 60 b can be disposed more densely than the catalyst 25 of thefirst layer 60 a. By this means, when porosity is defined with the aboveequation (1), the second layer 60 b can be formed to a lower densitythan the first layer 60 a.

In FIG. 8D, before the second layer 60 b of the positive electrode layer60 has dried, a coater 45 is moved over the second layer 60 b as shownby the arrow [2], and a solution for making the ion exchange film 21 isapplied to the second layer 60 b to form the ion exchange film 21.

Here, because as mentioned above the porosity of the second layer 60 bhas been set lower than the porosity of the first layer 60 a, permeationof the solution of the ion exchange film 21 into the second layer 60 bis suppressed. By this means, the pores of the positive electrode layer60 are prevented from being diminished by the solution for making theion exchange film 21.

Here, the porosity of the second layer 60 b is set to at least 70% sothat the intimacy of the ion exchange film 21 and the second layer 60 bis kept good. The porosity of the second layer 60 b is set to below 75%to provide pores which can drain product water well.

Also, the porosity of the first layer 60 a is set to at least 76% toprovide pores for draining product water well, and the porosity of thefirst layer 60 a is set to below 85% to suppress resistance overvoltageand make it possible for current to be generated efficiently.

In FIG. 8E, before the ion exchange film 21 has dried, the sprayer 43 ismoved over the ion exchange film 21 as shown by the arrow [3], and thesolution for making the negative electrode layer 19 is applied to theion exchange film 21 through the spray nozzle 44. By this means, thenegative electrode layer 19 is formed on the ion exchange film 21.

In FIG. 8F, before the negative electrode layer 19 has dried, a solutionof the binder layer 15 of the negative electrode side diffusion layer 13(see FIG. 7) is applied to the negative electrode layer 19.

In FIG. 8G, a negative electrode side carbon paper 14 is placed on thebinder layer 15, so that the binder layer 15 and the carbon paper 14form a sheet-form negative electrode side diffusion layer 13.

Next, before the binder layer 18, the positive electrode layer 60, theion exchange film 21, the negative electrode layer 19 and the binderlayer 15 have dried, without a load being applied to the binder layer18, the positive electrode layer 60, the ion exchange film 21, thenegative electrode layer 19 and the binder layer 15, the binder layer18, the positive electrode layer 60, the ion exchange film 21, thenegative electrode layer 19 and the binder layer 15 are dried together.

In FIG. 8H, by the binder layer 18, the positive electrode layer 60, theion exchange film 21, the negative electrode layer 19 and the binderlayer 15 being hardened, the binder layer 18, the positive electrodelayer 60, the ion exchange film 21, the negative electrode layer 19 andthe binder layer 15 are laminated integrally in a hardened state. Withthis, the manufacturing process of the fuel cell electrode 62 shown inFIG. 7 is finished.

Thus, with the method for manufacturing the fuel cell electrode 62 ofthe second embodiment, by the solutions being applied to the respectiveupper faces with the binder layer 18, the positive electrode layer 60,the ion exchange film 21, the negative electrode layer 19 and the binderlayer 15 in an undried state, the solutions adjacent at the respectiveinterfaces can be made to mix well.

By this means it is possible to prevent areas of defective intimacyarising at the interface between the binder layer 18 and the positiveelectrode layer 60 (the first layer 60 a and the second layer 60 b).Also, it is possible to prevent areas of defective intimacy arising atthe interface between the positive electrode layer 60 and the ionexchange film 21. And also, it is possible to prevent areas of defectiveintimacy arising at the interface between the ion exchange film 21 andthe negative electrode layer 19. Additionally, it is possible to preventareas of defective intimacy arising at the interface between thenegative electrode layer 19 and the binder layer 15. By this means it ispossible to keep the reaction efficiency in the fuel cell electrode 62good.

Additionally, as a result of the ion exchange film 21 being made asolution, because the ion exchange film 21 can be handled in the form ofa solution, it is not necessary for the thickness of the ion exchangefilm 21 to be restricted from the point of view of handlability.Consequently, the ion exchange film 21 can be made thin, and the fuelcell electrode 62 can be made thin.

Next, a fuel cell electrode of a third embodiment will be described, onthe basis of FIG. 9. Parts the same as in the fuel cell electrode of thesecond embodiment shown in FIG. 7 have been given the same referencenumerals and will not be described again.

The fuel cell electrode 72 of the third embodiment has a positiveelectrode layer 70 (a first electrode layer) and a negative electrodelayer 19 (a second electrode layer) respectively on the inner sides of apositive electrode side diffusion layer 16 and a negative electrode sidediffusion layer 13, and has an ion exchange film 21 between the negativeelectrode layer 19 and the positive electrode layer 70. That is, onlythe positive electrode layer 70 of the fuel cell electrode 72 of thethird embodiment is different compared to the fuel cell electrode 62 ofthe second embodiment, and the rest of its construction is the same asthe second embodiment. The positive electrode layer 70 will be describedbelow.

The positive electrode layer 70 is divided into a first layer 70 a onthe side away from the ion exchange film 21 (i.e. the side in contactwith the positive electrode side diffusion layer 16) and a second layer70 b on the side in contact with the ion exchange film 21, and whenporosity is defined by the following equation (1), the second layer 70 bhas a lower porosity than the first layer 70 a.POROSITY=(1−BULK S. G./TRUE S. G.)×100   (1)

The first layer 70 a, like the first layer 60 a of the second embodimentshown in FIG. 7, is made by mixing a catalyst 25 with a solution formaking the first layer 70 a and hardening the solution by drying itafter it is applied. The catalyst 25 of the first layer 70 a is one madeby attaching platinum 27 as a catalyst to the surface of carbon 26, andoxygen molecules (O₂) are adsorbed onto this platinum 27. The particlesize of this carbon 26 is D1.

The second layer 70 b is made by mixing a catalyst 71 with a solutionfor making the second layer 70 b and hardening the solution by drying itafter it is applied. The catalyst 71 of the second layer 70 b is onemade by attaching platinum 74 as a catalyst to the surface of carbon 73,and oxygen molecules (O₂) are adsorbed onto this platinum 74. Theparticle size of this carbon (electrode) 73 is D2. This particle size D2is smaller than the particle size D1 of the carbon 26 of the first layer70 a.

By the particle size D2 of the carbon 73 of the second layer 70 b beingset smaller than the particle size Di of the carbon 26 of the firstlayer 70 a like this, compared to the carbon 26 of the first layer 70 a,the carbon 73 of the second layer 70 b can be disposed more densely. Bythis means, the porosity of the second layer 70 b can be made lower thanthat of the first layer 70 a. Specifically, the porosity of the secondlayer 70 b is made 70 to 75% and the porosity of the first layer 70 a ismade 76 to 85%.

The reasons for the porosity of the second layer 70 b being made 70 to75% and the porosity of the first layer 70 a being made 76 to 85% arethe same as the reasons for the porosity of the second layer 60 b of thesecond embodiment described with reference to FIG. 7 being made 70 to75% and the porosity of the first layer 60 a being made 76 to 85%, andwill not be explained again here.

Next, a method of manufacturing the fuel cell electrode 72 of the thirdembodiment shown in FIG. 9 will be described, on the basis of FIG. 10Athrough FIG. 10I.

In FIG. 10A, the sheet-form positive electrode side diffusion layer 16is laid. That is, the carbon paper 17 of the positive electrode sidediffusion layer 16 is set, and a solution for making the binder layer 18is applied to this carbon paper 17.

In FIG. 10B, before the binder layer 18 has dried, a sprayer 75 is movedover the binder layer 18 as shown by the arrow [4], and a solution formaking the first layer 70 a of the positive electrode layer 70 isapplied to the binder layer 18 through a spray nozzle 75 a. By thismeans, the first layer 70 a is formed on the binder layer 18.

Here, when porosity is defined by the foregoing equation (1), theporosity of the first layer 70 a is made 76 to 85%.

In FIG. 10C and FIG. 10D, before the first layer 70 a has dried, asprayer 76 is moved over the first layer 70 a in the direction of thearrow [5], and a solution for making the second layer 70 b of thepositive electrode layer 70 is applied through a spray nozzle 76 a. Bythis means, the second layer 70 b is formed on the first layer 70 a.Here, by the particle diameter D2 of the carbon 73 being set smallerthan the particle diameter D1 of the carbon 26 of the first layer 70 a,the carbon 73 of the second layer 70 b can be disposed more denselycompared to the carbon 26 of the solution of the first layer 70 a. Bythis means it is possible to make the porosity of the second layer 70 bsmaller than that of the first layer 70 a. That is, the catalyst 71 ofthe second layer 70 b can be disposed more densely than the catalyst 25of the first layer 70 a. Specifically, when porosity is defined by theforegoing equation (1), the porosity of the second layer 70 b is made 70to 75%.

In FIG. 10E, before the second layer 70 b of the positive electrodelayer 70 has dried, a coater 77 is moved over the second layer 70 b asshown by the arrow [6], and a solution for making the ion exchange film21 is applied to the second layer 70 b to form the ion exchange film 21.

At this stage, the positive electrode layer 70 is divided into twolayers, the first layer 70 a on the side away from the ion exchange film21 and the second layer 70 b on the side in contact with the ionexchange film 21, and the porosity of the second layer 70 b is made 70to 75% and the porosity of the first layer 70 a is made 76 to 85%, sothat the porosity of the second layer 70 b is lower than the porosity ofthe first layer 70 a. By the porosity of the second layer 70 b beingmade low like this, permeation of the solution of the ion exchange film21 into the first layer 70a can be suppressed, and permeation of thesolution for making the ion exchange film 21 into the second layer 70 bcan be kept down. By this means, the solution for making the ionexchange film 21 can be prevented from diminishing the porosity of thepositive electrode layer 70.

When the porosity of the second layer 70 b is above 70%, the intimacy ofthe ion exchange film 21 and the second layer 70 b can be kept good, andwhen the porosity of the second layer 70 b is below 75%, the productwater can be drained well.

The porosity of the first layer 70 a is set to above 76% to providepores for draining product water well, and the porosity of the firstlayer 70 a is set to below 85% to suppress resistance overvoltage andenable current to be generated well.

In FIG. 10F, before the ion exchange film 21 has dried, a sprayer 78 ismoved over the ion exchange film 21 as shown by the arrow [7], and asolution for making the negative electrode layer 19 is applied to theion exchange film 21 through a spray nozzle 78 a. By this means, thenegative electrode layer 19 is formed on the ion exchange film 21.

In FIG. 10G, before the negative electrode layer 19 has dried, asolution of the binder layer 15 of the negative electrode side diffusionlayer 13 (see FIG. 9) is applied to the negative electrode layer 19.

In FIG. 10H, a negative electrode side carbon paper 14 is placed on thebinder layer 15 so that a negative electrode side diffusion layer 13 isformed by the binder layer 15 and the carbon paper 14.

Next, before the binder layer 18, the positive electrode layer 70, theion exchange film 21, the negative electrode layer 19 and the binderlayer 15 have dried, without a load being applied to the binder layer18, the positive electrode layer 70, the ion exchange film 21, thenegative electrode layer 19 or the binder layer 15, the binder layer 18,the positive electrode layer 70, the ion exchange film 21, the negativeelectrode layer 19 and the binder layer 15 are dried together.

In FIG. 10I, by the binder layer 18, the positive electrode layer 70,the ion exchange film 21, the negative electrode layer 19 and the binderlayer 15 being hardened, the binder layer 18, the positive electrodelayer 70, the ion exchange film 21, the negative electrode layer 19 andthe binder layer 15 are laminated integrally in a hardened state. Withthis, the manufacturing process of the fuel cell electrode 72 isfinished.

Thus, with the method for manufacturing the fuel cell electrode 72 ofthe third embodiment, by the solutions being applied to the respectiveupper faces with the binder layer 18, the positive electrode layer 70,the ion exchange film 21, the negative electrode layer 19 and the binderlayer 15 in an undried state, the solutions adjacent at the respectiveinterfaces can be made to mix well. By this means it is possible toprevent areas of defective intimacy arising at the interface between thebinder layer 18 and the positive electrode layer 70 (the first layer 70a and the second layer 70 b). Also, it is possible to prevent areas ofdefective intimacy arising at the interface between the positiveelectrode layer 70 and the ion exchange film 21. Also, it is possible toprevent areas of defective intimacy arising at the interface between theion exchange film 21 and the negative electrode layer 19. Additionally,it is possible to prevent areas of defective intimacy arising at theinterface between the negative electrode layer 19 and the binder layer15, and the reaction efficiency in the fuel cell electrode 72 can bekept good.

Although in the second and third embodiments examples were describedwherein the positive electrode layer 60, 70 is disposed below and thenegative electrode layer 19 is disposed above, the same effects can beobtained by disposing the positive electrode layer 60, 70 above anddisposing the negative electrode layer 19 below.

Although examples were described such that in the manufacture of theelectrode of the second embodiment the first and second layers 60 a, 60b of the positive electrode layer 60 were applied with a spray and inthe manufacture of the electrode of the third embodiment the first andsecond layers 70 a, 70 b of the positive electrode layer 70 were appliedwith a spray, the layers do not have to be sprayed and can alternativelybe applied using the ink jet method. In short, any method by which thesolutions for making the layers can be applied in spray form willsuffice.

FIG. 11 shows the cross-sectional structure of a fuel cell electrode 112of a fourth embodiment of the invention. Parts the same as in the fuelcell electrode of the first embodiment have been given the samereference numerals.

The fuel cell electrode 112 of this fourth embodiment has a negativeelectrode layer 19 and a positive electrode layer 20 on the inner sidesof a negative electrode side diffusion layer 113 and a positiveelectrode side diffusion layer 116 respectively, and has an ion exchangefilm 21 between the negative electrode layer 19 and the positiveelectrode layer 20.

The positive electrode side diffusion layer 116 is a sheet made up of apositive electrode side carbon paper 117, which is one carbon paper, anda positive electrode side binder layer 118, which is one binder layer.

The negative electrode side diffusion layer 113 is a sheet made up of anegative electrode side carbon paper 114, which is the other carbonpaper, and a negative electrode side binder layer 115, which is theother binder layer.

The solution of the negative electrode side binder layer 115 includesfor example granular carbon 115 a and an ion exchange resin serving asan adhesive resin 115 b with good adhesion. The ion exchange resinserving as the adhesive resin 115 b is for example a perfluoro ionexchange resin. Examples of this perfluoro ion exchange resin includethose marketed as trade name “Nafion” made by DuPont, trade name“Flemion” made by Asahi Glass Company and trade name “Aciplex” made byAsahi Kasei.

The reason for including an adhesive resin 115 b in the negativeelectrode side binder layer 115 is as follows.

That is, in the manufacture of the fuel cell electrode 112, for examplethe positive electrode layer 20, the ion exchange film 21 and thenegative electrode layer 19 are layered in turn on the positiveelectrode side binder layer 118, and the negative electrode side binderlayer 115 is layered on the negative electrode layer 19. Therefore, toraise the adhesion between the negative electrode side carbon paper 114and the negative electrode side binder layer 115, a pressing process isnecessary, but by an adhesive resin 115 b being included in the negativeelectrode side binder layer 115, the intimacy of the negative electrodeside carbon paper 114 and the negative electrode side binder layer 115is kept good.

The reason for using an ion exchange resin as the adhesive resin 115 bis as follows.

That is, by employing an ion exchange resin as the adhesive resin 115 b,the solution of the negative electrode side binder layer 115 is made thesame kind of substance as the solution of the negative electrode layer19. By this means the ion exchange resin included in the solution of thenegative electrode side binder layer 115 and the ion exchange resinincluded in the solution of the negative electrode layer 19 can be mixedwell and the intimacy between the negative electrode side binder layer115 and the negative electrode layer 19 can be kept good.

The solution of the positive electrode side binder layer 118 has forexample granular carbon 118 a, a vinylidenefluoride/tetrafluoroethylene/hexafluoro-propylene copolymer serving as aresin 118 b excellent in water repellency, and water serving as asolvent.

The melting point of the water repellent resin 118 b of the positiveelectrode side binder layer 118 is set to below 150° C. When the meltingpoint of the water repellent resin 118 b exceeds 150° C., there is arisk of the temperature being too high and it consequently not beingpossible to fire the water repellent resin 118 b together with thepositive and negative electrode layers 20, 19 and the ion exchange film21.

Accordingly, by the water repellent resin 118 b being made a resin witha low melting point not higher than 150° C., the water repellent resin118 b can be dried together with the negative electrode side binderlayer 115, the positive and negative electrode layers 20, 19 and the ionexchange film 21 after the negative electrode side binder layer 115, thepositive and negative electrode layers 20, 19 and the ion exchange film21 are stacked.

An example of the water repellent resin (low-melting-point resin) 118 bof melting point below 150° C. is the above-mentioned vinylidenefluoride/tetrafluoroethylene/hexafluoropropylene copolymer. Vinylidenefluoride/tetrafluoroethylene/hexafluoropropylene copolymer has theproperty of dispersing in water as a solvent. This vinylidenefluoride/tetrafluoroethylene/hexafluoropropylene copolymer, after thewater serving as the solvent has evaporated, reaches its melting pointand melts, and exhibits a water repellent effect.

Preferably, the melting point of the water repellent resin 118 b of thepositive electrode side binder layer 118 is set to above 100° C. Thatis, because vinylidene fluoride/tetrafluoroethylene/hexafluoropropylenecopolymer does not dissolve in water, when water is used as the solvent,to dry off the water and melt the vinylidenefluoride/tetrafluoroethylene/hexafluoropropylene copolymer a meltingpoint of at least 100° C. is necessary.

The solution of the positive electrode side binder layer 118 includeswater serving as a solvent. Because water has excellent dispersingpower, by using water as the solvent, the water repellent resin(low-melting-point resin) 118 b and the carbon 118 a can be made to mixwell in the water.

By this means, the solution for making the positive electrode sidebinder layer 118 can be applied to the positive electrode side carbonpaper 117 in a spray state by a sprayer or an ink jet or the like.Consequently, the solution for making the positive electrode side binderlayer 118 can be applied well to the depressions in the positiveelectrode side carbon paper 117, whose surface is irregular.

Thus, the solution for making the positive electrode side binder layer118 can be applied well over the whole surface of the positive electrodeside carbon paper 117, the water repellent resin 118 b can be made topermeate the whole surface of the positive electrode side carbon paper117, and the water repellency of the positive electrode side carbonpaper 117 can be increased.

Also, the negative electrode layer 19 of the fuel cell electrode 112 ismade by mixing a catalyst 22 with the solution for making the negativeelectrode and hardening the solution by drying it after it is applied.The catalyst 22 of the negative electrode layer 19 is one made byattaching a platinum-ruthenium alloy 24 as a catalyst to the surface ofcarbon 23, and hydrogen molecules (H₂) are adsorbed onto theplatinum-ruthenium alloy 24.

The positive electrode layer 20 is made by mixing a catalyst 25 with thesolution for making the positive electrode and hardening the solution bydrying it after it is applied. The catalyst 25 of the positive electrodelayer 20 is one made by attaching platinum 27 as a catalyst to thesurface of carbon 26, and oxygen molecules (O₂) are adsorbed onto thisplatinum 27.

The ion exchange film 21 is formed by applying a solution between thenegative electrode layer 19 and the positive electrode layer 20 and thenhardening it integrally with the negative electrode layer 19 and thepositive electrode layer 20 by drying it together with the negativeelectrode layer 19 and the positive electrode layer 20.

Next, a method for manufacturing the fuel cell electrode 112 of thefourth embodiment shown in FIG. 11 will be described, on the basis ofFIG. 12A through FIG. 12G.

In FIG. 12A, a sheet-form positive electrode side diffusion layer 116 islaid. That is, a positive electrode side carbon paper 117 of thepositive electrode side diffusion layer 116 is set, and then by asprayer 151 being moved over the positive electrode side carbon paper117 in the direction of the arrow while the solution for making thepositive electrode side binder layer 118 is sprayed in an atomized statethrough a spray nozzle 115 a of the sprayer 151, the positive electrodeside binder layer 118 is formed.

Here, because water, which has excellent dispersing power, is includedas a solvent in the solution of the positive electrode side binder layer118, the low-melting-point resin 118 b and the granular carbon 118 a canbe mixed well with the solvent. As a result, the solution for making thepositive electrode side binder layer 118 can be applied in an atomizedstate, and the solution for making the positive electrode side binderlayer 118 can be applied well to the depressions in the surface of thepositive electrode side carbon paper 117.

Consequently, as shown in FIG. 12A, the solution for making the positiveelectrode side binder layer 118 can be applied well to the whole surfaceof the positive electrode side carbon paper 117. As a result, the waterrepellent resin 118 b is made to permeate into the whole surface of thepositive electrode side carbon paper 117, and the water repellency ofthe positive electrode side carbon paper 117 is increased.

In FIG. 12B, before the positive electrode side binder layer 118 hasdried, the solution of the positive electrode layer 20 is applied to thepositive electrode side binder layer 118 to form the positive electrodelayer 20. By this means, the interface between the positive electrodeside binder layer 118 and the positive electrode layer 20 can be mixedwell and its intimacy raised.

In FIG. 12C, before the positive electrode layer 20 has dried, thesolution of the ion exchange film 21 is applied to the positiveelectrode layer 20 to form the ion exchange film 21. By this means, theinterface between the positive electrode layer 20 and the ion exchangefilm 21 can be mixed well and its intimacy raised.

In FIG. 12D, before the ion exchange film 21 as dried, the solution ofthe negative electrode layer 19 is applied to the ion exchange film 21to form the negative electrode layer 19. By this means, the interfacebetween the ion exchange film 21 and the negative electrode layer 19 canbe mixed well and its intimacy raised.

In FIG. 12E, before the negative electrode layer 19 has dried, thesolution for making the negative electrode side binder layer 115 isapplied to the negative electrode layer 19 to form the negativeelectrode side binder layer 115. By this means, the interface betweenthe negative electrode layer 19 and the negative electrode side binderlayer 115 can be mixed well and its intimacy raised.

Here, an ion exchange resin is included in the solution of the negativeelectrode side binder layer 115 as an adhesive resin 115b with goodadhesion. This ion exchange resin is the same kind of material as theion exchange resin included in the solution of the negative electrodelayer 19, and the ion exchange resin included in the solution of thenegative electrode side binder layer 115 can be mixed well with the ionexchange resin included in the solution of the negative electrode layer19. By this means, even without the weight of the positive electrodelayer 20, the ion exchange film 21 and the negative electrode layer 19acting upon the negative electrode side binder layer 115, the intimacybetween the negative electrode side binder layer 115 and the negativeelectrode layer 19 can be kept good like the intimacy between thepositive electrode side binder layer 118 and the positive electrodelayer 20.

In FIG. 12F, by the negative electrode side carbon paper 114 beingplaced on the negative electrode side binder layer 115, a sheet-formnegative electrode side diffusion layer 113 is formed with the negativeelectrode side binder layer 115 and the negative electrode side carbonpaper 114.

Next, in drying of the positive and negative electrode layers 20, 19 andthe ion exchange film 21 without a load being applied to the positiveelectrode side binder layer 118, the positive and negative electrodelayers 20, 19, the ion exchange film 21 and the negative electrode sidebinder layer 115 (that is, without them being heated and compressed asin related art), the positive electrode side binder layer 118 and thenegative electrode side binder layer 115 are fired together.

As a result of the water repellent resin 118 b of the positive electrodeside binder layer 118 being made a resin with a low melting point below150° C., when the positive and negative electrode layers 20, 19 and theion exchange film 21 are dried, the positive electrode side binder layer118 and the negative electrode side binder layer 115 can be firedtogether in one go. Consequently, because the related art drying step offiring only the positive electrode side binder layer 118 can beeliminated, the number of drying steps can be reduced and the fuel cellelectrode can be manufactured efficiently.

In FIG. 12G, the positive electrode side binder layer 118, the positiveelectrode layer 20, the ion exchange film 21, the negative electrodelayer 19 and the negative electrode side binder layer 115 are laminatedintegrally in a hardened state. With this, the manufacturing process ofthe fuel cell electrode 112 of the fourth embodiment shown in FIG. 11ends.

As explained above, with the manufacturing method of the fuel cellelectrode 112 of the fourth embodiment, by employing a solution for theion exchange film 21 and applying the solution for making the ionexchange film 21 to the positive electrode layer 20 before the positiveelectrode layer 20 has dried, at the interface between the positiveelectrode layer 20 and the ion exchange film 21 their solutions can bemade to mix effectively.

Further, by applying the solution for the negative electrode layer 19 tothe ion exchange film 21 before the ion exchange film 21 has dried, atthe interface between the ion exchange film 21 and the negativeelectrode layer 19 their solutions can be made to mix effectively.

By the positive and negative electrode layers 20, 19 and the ionexchange film 21 being dried together in one go, they can be hardenedwith the interfaces between the positive and negative electrode layers20, 19 and the ion exchange film 21 mixed effectively. By this means,areas of defective intimacy can be prevented from arising at the layerinterfaces of the positive and negative electrode layers 20, 19 and theion exchange film 21, and consequently the reaction efficiency at theion exchange film 21 can be kept good. By this means, the reactionefficiency in the fuel cell electrode 112 can be kept good.

Additionally, because as a result of the ion exchange film 21 being madea solution the ion exchange film 21 can be handled in the form of asolution, it is not necessary for the thickness of the ion exchange film21 to be regulated from the handling point of view. Consequently, theion exchange film 21 can be made thin, and the fuel cell electrode 112can be made thin.

FIG. 13 shows the cross-sectional structure of a fuel cell electrode 212of a fifth embodiment of the invention. Parts the same as in the fuelcell electrode of the fourth embodiment shown in FIG. 11 have been giventhe same reference numerals.

The fuel cell electrode 212 of this fifth embodiment has a negativeelectrode layer 19 and a positive electrode layer 20 on the inner sidesof a negative electrode side diffusion layer 113 and a positiveelectrode side diffusion layer 216 respectively, and has an ion exchangefilm 21 between the negative electrode layer 19 and the positiveelectrode layer 20.

The positive electrode side diffusion layer 216 is a sheet made up of apositive electrode side carbon paper 217, which is a first carbon paper,and a positive electrode side binder layer 218, which is a first binderlayer.

The solution of the positive electrode side binder layer 218 includesfor example granular carbon 218 a and a resin which is soluble in anorganic solvent and is water repellent (hereinafter called “waterrepellent resin”) 218 b.

As the water repellent resin 218 b, a resin of one or a plurality oftypes chosen from among vinylidenefluoride/tetrafluoroethylene/hexafluoropro-pylene copolymers,polyvinylidene fluoride (PVDF), fluoro-olefin/hydrocarbon-olefincopolymers, fluoro-acrylate copolymers, and fluoro-epoxy compounds isused.

Because a vinylidene fluoride/tetrafluoroethylene/hexafluoropropylenecopolymer, polyvinylidene fluoride (PVDF),fluoro-olefin/hydrocarbon-olefin copolymer, fluoro-acrylate copolymer,or fluoro-epoxy compound serving as the water repellent resin 218 b hasthe property of dissolving in an organic solvent included in thesolution of the positive electrode side binder layer 218, it enables theinvention to be worked well.

Here, the organic solvent may be of for example at least one type amongalcohol solvents, ketone solvents, and ester solvents.

Because an organic solvent included in the solution for making thepositive electrode side binder layer 218 has excellent dissolving power,by using an organic solvent it is possible to dissolve the waterrepellent resin 218 b well in the organic solvent. The carbon 218 a isdispersed or mixed in the organic solvent.

Next, a method of manufacturing the fuel cell electrode 212 of thisfifth embodiment will be described, on the basis of FIG. 14A, FIG. 14Band FIG. 14C.

In FIG. 14A, the sheet-form positive electrode side diffusion layer 216is laid. That is, a positive electrode side carbon paper 217 of thepositive electrode side diffusion layer 216 is set, and by a sprayer 151being moved over the positive electrode side carbon paper 217 in thedirection of the arrow while the solution for making the positiveelectrode side binder layer 218 is sprayed in an atomized state througha spray nozzle 151a of the sprayer 151, the positive electrode sidebinder layer 218 is formed.

Here, because an organic solvent having good dissolving power isincluded in the solution of the positive electrode side binder layer218, the water repellent resin 218 b can be dissolved well with theorganic solvent. As a result, the solution for making the positiveelectrode side binder layer 218 can be applied in an atomized state, andthe solution for making the positive electrode side binder layer 218 canbe applied well to the depressions in the surface of the positiveelectrode side carbon paper 217.

Consequently, the solution for making the positive electrode side binderlayer 218 can be applied well to the whole surface of the positiveelectrode side carbon paper 217. By this means, the water repellentresin 218b is made to permeate into the whole surface of the positiveelectrode side carbon paper 217, and the water repellency of thepositive electrode side carbon paper 217 is increased.

In FIG. 14B, before the positive electrode side binder layer 218 hasdried, the solution of the positive electrode layer 20 is applied to thepositive electrode side binder layer 218 to form the positive electrodelayer 20. By this means, the interface between the positive electrodeside binder layer 218 and the positive electrode layer 20 can be mixedwell and its intimacy raised.

In FIG. 14C, in the same way as in the manufacturing method for the fuelcell electrode of the fourth embodiment, before the positive electrodelayer 20 has dried, the solution of the ion exchange film 21 is appliedto the positive electrode layer 20 to form the ion exchange film 21. Bythis means, the interface between the positive electrode layer 20 andthe ion exchange film 21 can be mixed well and its intimacy raised.

Thereafter, in the same way as the method shown in FIG. 12D through FIG.12G of the manufacturing method for the fuel cell electrode of thefourth embodiment, before the ion exchange film 21 has dried, thesolution for making the negative electrode layer 19 is applied to theion exchange film 21 to form the negative electrode layer 19.

Then, before the negative electrode layer 19 has dried, the solution ofthe negative electrode side binder layer 115 is applied to the negativeelectrode layer 19 to form the negative electrode side binder layer 115.Then, before the negative electrode side binder layer 115 has dried, thenegative electrode side carbon paper 114 is placed.

In this way, after the positive electrode side diffusion layer 216, thepositive and negative electrode layers 20, 19, the ion exchange film 21and the negative electrode side diffusion layer 113 are stacked, withouta load being applied to the positive electrode side binder layer 218,the positive and negative electrode layers 20, 19, the ion exchange film21 and the negative electrode side binder layer 115 (that is, withoutthem being heated and compressed as in related art), when the positiveand negative electrode layers 20, 19 and the ion exchange film 21 aredried, the positive electrode side binder layer 218 and the negativeelectrode side binder layer 115 are fired together.

Here, because the drying temperature of the organic solvent is likely tobe about 70 to 80° C., at the time of drying the positive and negativeelectrode layers 20, 19, or the ion exchange film 21 the organic solventcan be removed to leave the water repellent resin 218 b, and the waterrepellent resin 218 b can be fired together with the rest. By thismeans, as in the manufacturing method for the fuel cell electrode of thefourth embodiment, because it is possible to eliminate the drying stepof firing only the positive electrode side binder layer 218, which hasbeen necessary in related art, the number of drying steps can be reducedand the fuel cell electrode can be manufactured efficiently.

With the manufacturing method of the embodiment described above, byincluding an organic solvent with superior dissolving power in thesolution for making the positive electrode side binder layer 218, it ispossible to dissolve the water repellent resin 218b well in the organicsolvent.

Also, because the water repellent resin 218 b can be fired at the sametime as the positive and negative electrode layers 20, 19 and the ionexchange film 21 are being dried, the solution of the positive electrodelayer 20 can be applied to the positive electrode side diffusion layer216 before the water repellent resin 218 b (that is, the positiveelectrode side diffusion layer 216) has dried, and the interface of thepositive electrode side diffusion layer 216 and the positive electrodelayer 20 can be mixed well.

Furthermore, by using an organic solvent with good dissolving power, itis possible to dissolve the water repellent resin 218 b well in theorganic solvent. Consequently it is possible to apply the solution formaking the positive electrode side binder layer 218 in an atomized statewith a sprayer or an ink jet or the like, and the solution for makingthe positive electrode side binder layer 218 can be applied well even tothe depressions in the surface of the positive electrode side carbonpaper 217. Accordingly, because the solution for making the positiveelectrode side binder layer 218 can be applied well to the whole surfaceof the positive electrode side carbon paper 217, the water repellentresin 218 b can be made to permeate into the whole surface of thepositive electrode side carbon paper 217, and the water repellency ofthe positive electrode side carbon paper 217 can be improved.

Although in the manufacturing methods of the fuel cell electrodes of thefourth and fifth embodiments examples were described wherein thepositive electrode side diffusion layer 116, 216 was disposed below andthe negative electrode side diffusion layer 113 was disposed above, itis also possible for the negative electrode side diffusion layer 113 tobe disposed below and for the positive electrode side diffusion layer116, 216 to be disposed above. In this case, the adhesive resin 115 bwhich was included in the negative electrode side binder layer 115 isincluded in the positive electrode side binder layer 118, 218. By theadhesive resin 115 b being included in the positive electrode sidebinder layer 118, 218 like this, the intimacy of the positive electrodeside carbon paper 117, 217 and the positive electrode side binder layer118, 218 can be kept good.

FIG. 15 shows the cross-sectional structure of a fuel cell electrode ofa sixth embodiment of the invention. Parts the same as in the fuel cellelectrode of the first embodiment shown in FIG. 2 have been given thesame reference numerals.

This fuel cell electrode 312 has a negative electrode layer 19 and apositive electrode layer 20 on the inner sides of a negative electrodeside diffusion layer 313 and a positive electrode side diffusion layer316 respectively, and has an ion exchange film 21 between the negativeelectrode layer 19 and the positive electrode layer 20.

The negative electrode side diffusion layer 313 is a sheet made up of anegative electrode side carbon paper 314 and a negative electrode sidebinder layer 315.

The positive electrode side diffusion layer 316 is a sheet made up of apositive electrode side carbon paper 317 and a positive electrode sidebinder layer 318.

The negative electrode side binder layer 315 is a layer having forexample granular carbon 315 a and a water repellent resin (for example afluoropolymer) 315 b, with an upper face 315 c adjacent to the negativeelectrode layer 19 formed flat.

The positive electrode side binder layer 318 has for example a granularcarbon 318 a and a water repellent resin (for example a fluoropolymer)318 b.

The negative electrode layer 19 is made by mixing a catalyst 22 with thesolution for making the negative electrode and hardening the solution bydrying it after it is applied. The catalyst 22 of the negative electrodelayer 19 is one made by attaching a platinum-ruthenium alloy 24 as acatalyst to the surface of carbon 23, and hydrogen molecules (H₂) areadsorbed onto the platinum-ruthenium alloy 24.

The positive electrode layer 20 is made by mixing a catalyst 25 with thesolution for making the positive electrode and hardening it by dryingthe solution after it is applied. The catalyst 25 of the positiveelectrode layer 20 is one made by attaching platinum 27 as a catalyst tothe surface of carbon 26, and oxygen molecules (O₂) are adsorbed ontothis platinum 27.

The ion exchange film 21 is formed by applying a solution between thenegative electrode layer 19 and the positive electrode layer 20 and thenhardening it integrally with the negative electrode layer 19 and thepositive electrode layer 20 by drying it together with the negativeelectrode layer 19 and the positive electrode layer 20.

Next, a method for manufacturing the fuel cell electrode 312 of thesixth embodiment of the invention will be described, on the basis ofFIG. 16A through FIG. 16H.

In FIG. 16A, the sheet-form negative electrode side diffusion layer 313is laid. That is, the carbon paper 314 of the negative electrode sidediffusion layer 313 is set, and then a sprayer 351 is moved over thecarbon paper 314 as shown by the arrow [1] while the binder (that is,the carbon 315 a and the fluoropolymer 315 b) is sprayed from a spraynozzle 351 a of the sprayer 351.

Here, the upper face of the carbon paper 314 is formed as an irregularsurface, but by using the sprayer 351 it is possible to atomize thecarbon 315 a and the fluoropolymer 315 b and apply them to the upperface of the carbon paper 314, and the carbon 315 a and the fluoropolymer315 b can be applied surely even to depressions in the carbon paper 314.By this means, the fluoropolymer 315 b can be made to permeate into thewhole area of the carbon paper 314, and a water repellent effect isobtained over the whole area of the carbon paper.

In FIG. 16B, before the binder layer 315 has. dried, while a roller 354is rotated along the upper face 315 c of the binder layer 315 as shownby the arrow [2], the roller 354 is moved as shown by the arrow [3]. Asa result, the upper face 315 c of the binder layer 315 becomes flat.

In FIG. 16C, to the negative electrode side binder layer 315. with itsupper face flattened, before the binder layer 315 has dried, thesolution of the negative electrode layer 19 is applied to form thenegative electrode layer 19. Because the negative electrode layer 19 isformed by applying the solution of the negative electrode layer 19 tothe upper face 315 c of a flattened negative electrode side binder layer315, the upper face of the negative electrode layer 19 is flat.

In FIG. 16D, before the negative electrode layer 19 has dried, by thesolution of the ion exchange film 21 being applied, the ion exchangefilm 21 is formed. Because the ion exchange film 21 is formed byapplying the solution of the ion exchange film 21 to a flat negativeelectrode layer 19, the upper face of the ion exchange film 21 is flat.

In FIG. 16E, to the ion exchange film 21 with the flat upper face,before the ion exchange film 21 has dried, the solution of the positiveelectrode layer 20 is applied to form the positive electrode layer 20.Because the positive electrode layer 20 is formed by applying thesolution of the positive electrode layer 20 to a flat ion exchange film21, the upper face of the positive electrode layer 20 is flat.

Because the ion exchange film 21 can be formed flat like this, thepositive electrode layer 20 applied to the top of the ion exchange film21 and the negative electrode layer 19 applied to the bottom of the ionexchange film 21 can be kept apart surely, and shorting of the positiveelectrode layer 20 and the negative electrode layer 19 can be prevented.

In FIG. 16F, to the positive electrode layer 20, before the positiveelectrode layer 20 has dried, the binder of the positive electrode sidebinder layer 318 (that is, the carbon 318 a and the fluoropolymer 318 b)are applied to form the positive electrode side binder layer 318.

In FIG. 16G, by the positive electrode side carbon paper 317 beingplaced on the positive electrode side binder layer 318, the sheet-formpositive electrode side diffusion layer 316 is formed with the positiveelectrode side binder layer 318 and the positive electrode side carbonpaper 317.

Next, before the negative electrode layer 19, the ion exchange film 21and the positive electrode layer 20 have dried, without a load beingapplied to the negative electrode layer 19, the ion exchange film 21 andthe positive electrode layer 20, the negative electrode layer 19, theion exchange film 21 and the positive electrode layer 20 are driedtogether.

In FIG. 16H, by the negative electrode layer 19, the ion exchange film21 and the positive electrode layer 20 being hardened, the negativeelectrode layer 19, the ion exchange film 21 and the positive electrodelayer 20 are laminated integrally. With this, the process ofmanufacturing the fuel cell electrode 312 of the sixth embodiment shownin FIG. 15 ends.

Thus, with the manufacturing method of the fuel cell electrode 312 ofthis sixth embodiment, by employing a solution for the ion exchange film21 and applying the solution for making the ion exchange film 21 to thenegative electrode layer 19 before the negative electrode layer 19 hasdried, at the interface of the negative electrode layer 19 and the ionexchange film 21 their solutions can be made to mix effectively.

And by the solution for making the binder layer 18 being applied to theion exchange film 21 before the ion exchange film 21 has dried, at theinterface of the ion exchange film 21 and the positive electrode layer20 their solutions can be made to mix effectively. And by the undriedpositive and negative electrode layers 20, 19 and the undried ionexchange film 21 being dried together all at once, they can be hardenedwith the interfaces of the positive and negative electrode layers 20, 19and the ion exchange film 21 mixed effectively. Therefore, areas ofdefective intimacy can be prevented from arising at the interfaces ofthe layers of the positive and negative electrode layers 20, 19 and theion exchange film 21, and the reaction efficiency in the ion exchangefilm 21 can be kept good. By this means, the reaction efficiency in thefuel cell electrode 312 can be kept good.

Next, another method for manufacturing the fuel cell electrode 312 ofthe sixth embodiment will be described, on the basis of FIG. 17A andFIG. 17B.

In FIG. 17A, in the same way as in the embodiment shown in FIG. 16A, thecarbon paper 314 of the negative electrode side diffusion layer 313 isset and then a sprayer 351 is moved over the carbon paper 314 as shownby the arrow [1] while the binder (that is, the carbon 315 a and thefluoropolymer 315 b) is sprayed from a spray nozzle 351 a of the sprayer351.

By using a sprayer 351 like this, it is possible to apply the carbon 315a and the fluoropolymer 315 b certainly even to depressions in thecarbon paper 314. By this means it is possible to make the fluoropolymer315 b permeate into the whole area of the carbon paper 314 and obtain awater repellent effect over the whole area of the carbon paper.

In FIG. 17B, before the negative electrode side binder layer 315 hasdried, by a presser plate 356 being pressed against the upper face 315 cof the negative electrode side binder layer 315 as shown by the arrow[4], the upper face 315 c of the negative electrode side binder layer315 can be flattened.

The means for making the upper face 315 c of the negative electrode sidebinder layer 315 flat are not limited to the roller 354 (see FIG. 16B)or the presser plate 356, and in this invention other means canalternatively be used.

Although in the sixth embodiment shown in FIG. 15 an example wasdescribed wherein the negative electrode layer 19 was disposed below andthe positive electrode layer 20 was disposed above, the same effects canbe obtained by disposing the negative electrode layer 19 above anddisposing the positive electrode layer 20 below.

Also, although in the method of the embodiment described above anexample was described wherein when the binder (that is, the carbon 315 aand the fluoropolymer 315 b) is spray-coated onto the upper face of thecarbon paper 314 the binder is applied in an atomized state by a sprayer351, instead of a sprayer some other spray-coating method such as an inkjet or the like can alternatively be employed.

A sprayer and an ink jet are the same in the point that they apply thesolution in an atomized state, but because in the case of a sprayer thescope is relatively wide and the application time can be made short, thesprayer is preferable.

FIG. 18 shows a fuel cell shown in exploded perspective view having afuel cell electrode pertaining to a seventh embodiment of the invention.

A fuel cell unit 400 is made up of a plurality of (in the example shownin the figure, two) fuel cells 411, 411. Each fuel cell 411 is made byproviding an ion exchange film for a fuel cell (simply called an ionexchange film) 414 on a negative pole (electrode) 412, superposing apositive pole (electrode) 416 on this ion exchange film 414, disposing anegative electrode side flow channel plate 421 on the outer side of thenegative electrode 412, and disposing a positive electrode side flowchannel plate 424 on the outer side of the positive electrode 416. Aplurality (two) of these fuel cells 411 are provided with a separator426 between them to constitute the fuel cell unit 400.

By the negative electrode side flow channel plate 421 being stackedagainst the negative electrode 412, flow channels 421a in the negativeelectrode side flow channel plate 421 are covered by the negativeelectrode 412, and hydrogen gas flow passages 422 are formed. By thepositive electrode side flow channel plate 424 being stacked against thepositive electrode 416, flow channels 424a in the positive electrodeside flow channel plate 424 are covered by the positive electrode 416,and oxygen gas flow passages 425 are formed.

By hydrogen gas being supplied to the hydrogen gas flow passages 422,hydrogen molecules (H₂) are adsorbed onto a catalyst included in thenegative electrode 412, and by oxygen gas being supplied to the oxygengas flow passages 425, oxygen molecules (O₂) are adsorbed onto acatalyst included in the positive electrode side diffusion layer 16. Asa result, electrons (e⁻) flow as shown by the arrow and a currentarises. When the current arises, product water (H₂O) is obtained fromthe hydrogen molecules (H₂) and oxygen molecules (O₂).

FIG. 19 shows the cross-sectional structure of the ion exchange film 414shown in FIG. 18, and shows the negative electrode 412 covered with theion exchange film 414.

The negative electrode 412 is a sheet formed from carbon paper in theshape of a polygon (for example an octagon); it includes a catalystinside it, and hydrogen molecules (H₂) are adsorbed onto this catalyst.Here, carbon paper means paper made from carbon fiber. The positiveelectrode 416 shown in FIG. 18 is a sheet formed of carbon like thenegative electrode 412; it includes a catalyst, and oxygen molecules(O₂) are adsorbed onto this catalyst.

The ion exchange film 414 is a polygonal (for example, octagonal) resinfilm obtained by applying a resin solution (hereinafter called “slurry”)to the surface 412 a of the negative electrode 412 and drying it afterapplication. As the resin solution, for example an HC polymer solutionis suitable. The “slurry” is a solution made by mixing the resin with aliquid.

FIG. 20 shows an ion exchange film forming apparatus 430.

The ion exchange film forming apparatus 430 has a bed 431 for placing anoctagonal negative electrode 412 (see FIG. 18 and FIG. 19) upon, a guideframe member 433 which surrounds the negative electrode 412 when set onthis bed 431, and an atomizer 440 above this guide frame member 433.

The bed 431 has plus charge imparting means 432 for imparting a pluscharge to the negative electrode 412.

The guide frame member 433 has an octagonal inner face 434 which followsthe periphery 412 b of the negative electrode 412 (see FIG. 19), has arecovery groove 435 running alongside this inner face 434, and has arecovery hole 436 formed so as to connect with this recovery groove 435.The inner face 434 is coated with a coating (not shown).

The atomizer 440 has a slurry nozzle 441. This slurry nozzle 441 issupported movably as shown by the arrow. The slurry nozzle 441 has minuscharge imparting means 442. Atomized slurry is sprayed from the end part441a of this slurry nozzle 441.

The shape of the mouth of the end part 441 a of the slurry nozzle 441 isformed so that the atomized slurry sprayed from the mouth forms anellipse.

The minus charge imparting means 442 imparts a minus charge to theatomized slurry sprayed from the slurry nozzle 441.

As the slurry nozzle 441 is moved from position P1 to position P4, overa first range E1 of from position P1 to position P2 (where the electrodeis narrow) the atomizer 440 is raised in a curve with an upward gradientas shown with an arrow, over a second range E2 of from position P2 toposition P3 (where the electrode is wide) it is moved horizontally asshown with an arrow, and over a third range E3 of from position P3 toposition P4 (where the electrode is narrow) it is lowered in a curvewith a downward gradient as shown with an arrow.

However, the movement of the slurry nozzle 441 is not limited to this,and may be set freely in accordance with the shape of the negativeelectrode 412.

FIG. 21 shows an ion exchange film forming apparatus according to theinvention.

While atomized slurry 451 is sprayed from the slurry nozzle 441, overthe first range E1 of from position P1 to position P2 the slurry nozzle441 is raised in a curve with an upward gradient as shown with an arrow,over the second range E2 of from position P2 to position P3 the slurrynozzle 441 is moved horizontally as shown with an arrow, and over thethird range E3 of from position P3 to position P4 the slurry nozzle 441is lowered in a curve with a downward gradient as shown with an arrow.

In the first range E1 of from position P1 to position P2, the width ofthe negative electrode 412 gradually increases as shown in FIG. 20 froma minimum width W1 to a maximum width W2. Because of this, as the slurrynozzle 441 is moved over the first range E1 of from position P1 toposition P2, the slurry nozzle 441 is raised in a curve with an upwardgradient as shown with an arrow from the position of height H1. By thismeans, the width of the atomized slurry sprayed from the slurry nozzle441 is changed in correspondence with the width of the negativeelectrode 412, and slurry can be prevented from projecting from thenegative electrode 412.

The sprayed amount of the atomized slurry 451 sprayed from the slurrynozzle 441 is increased along with the ascent of the slurry nozzle 441.By this means, the atomized slurry 451 can be applied uniformly to thenegative electrode 412.

In the second range E2 of from position P2 to position P3, as shown inFIG. 20 the width of the negative electrode 412 is constant at themaximum width W2. Because of this, as the slurry nozzle 441 is movedover the second range E2 of from position P2 to position P3, the slurrynozzle 441 is moved horizontally while being held at a maximum heightH2. By this means, the width of the atomized slurry sprayed from theslurry nozzle 441 can be widened in correspondence with the maximumwidth W2 of the negative electrode 412, and the maximum width W2 of thenegative electrode 412 can be coated with the atomized slurry.

In the second range E2, the sprayed amount of the atomized slurry 451sprayed from the slurry nozzle 441 is set to a maximum. By this means,the atomized slurry 451 can be applied uniformly to the negativeelectrode 412 in correspondence with the slurry on the first range E1.

In the third range E3 of from position P3 to position P4, as shown inFIG. 20 the width of the negative electrode 412 gradually decreases fromthe maximum width W2 to the minimum width W1. Because of this, as theslurry nozzle 441 is moved over the third range E3 of from position P3to position P4, the slurry nozzle 441 is lowered in a curve with adownward gradient as shown with an arrow from the maximum heightposition H2 to the position of the minimum height H1. By this means, thewidth of the atomized slurry sprayed from the slurry nozzle 441 ischanged in correspondence with the width of the negative electrode 412,and the atomized slurry 451 can be prevented from projecting from thenegative electrode 412 unnecessarily.

The sprayed amount of the atomized slurry 451 sprayed from the slurrynozzle 441 is decreased along with the descent of the slurry nozzle 441.By this means, the atomized slurry 451 can be applied uniformly to thenegative electrode 412 in correspondence with the slurry on the firstrange E1 and the second range E2.

By the height of the slurry nozzle 441 being adjusted in correspondencewith the width of the negative electrode 412 like this, for examplewhere the negative electrode 412 is narrow, the atomized slurry 451 canbe prevented from projecting from the negative electrode 412, and theatomized slurry 451 being applied to excess areas can be avoided.

Additionally, by the sprayed amount of the atomized slurry 451 beingchanged in correspondence with the variations in the height of theslurry nozzle 441, the slurry 452 can be applied to the surface 412 a ofthe negative electrode 412 to a uniform thickness. By this means thesurface of the ion exchange film 414 (see FIG. 19) can be made flat andthe quality of the fuel cell can be made stable.

When the slurry nozzle 441 is disposed in position P1 or position P4,the peripheral part 451 a of the atomized slurry 451 projects to outsidethe inner face 434 of the guide frame member 433; however, theprojecting peripheral part 451 a of the atomized slurry is recovered bythe recovery groove 435.

Next, a first method of forming an ion exchange film for a fuel cellwill be described, on the basis of FIG. 22A to FIG. 22J.

In FIG. 22A, the polygonal negative pole (electrode) 412 is formed fromcarbon paper, and the negative electrode 412 is placed on the bed 431.Then, the plus charge imparting means 432 is adjusted to impart a pluscharge to the negative electrode 412.

In FIG. 22B, the guide frame member 433 is disposed so as to surroundthe negative electrode 412. Then, the minus charge imparting means 442is adjusted to impart a minus charge to the atomized slurry 451 (seeFIG. 21) to be sprayed from the slurry nozzle 441.

In FIG. 22C, when the slurry nozzle 441 has moved horizontally from astandby position P0 as shown by the arrow [1] and reached a firstspraying position P1, the atomized slurry 451 is sprayed from the slurrynozzle 441.

In FIG. 22D, by the slurry nozzle 441 being disposed low so that its endpart 441 a is at a height H1 from the surface 412 a of the negativeelectrode 412, the width W3 of the atomized slurry 451 can be set sothat it is slightly greater than the width (minimum width) Wi of the endof the negative electrode 412, as shown in FIG. 22C. By this means, theatomized slurry 451 is prevented from projecting more than necessaryfrom the negative electrode 412.

The peripheral part of the atomized slurry 451 which projects to outsidethe inner face 434 of the guide frame member 433 is recovered by therecovery groove 435.

In FIG. 22E, with the atomized slurry 451 spraying from the slurrynozzle 441, the slurry nozzle 441 is moved from position P1 to positionP2 as shown by the arrow [2].

In FIG. 22F, because over the first range E1 of from position P1 toposition P2 the slurry nozzle 441 rises in a curve with an upwardgradient, the height H3 of the end part 441 a of the slurry nozzle 441gradually rises along with the movement of the slurry nozzle 441.Therefore, as shown in FIG. 22E, the width W5 of the atomized slurry 451sprayed from the slurry nozzle 441 can be gradually increased incorrespondence with the width W4 of the tapering part of the negativeelectrode 412. By this means, it is possible to avoid the atomizedslurry 451 projecting from the negative electrode 412 more thannecessary.

The peripheral part of the atomized slurry 451 which projects to outsidethe inner face 434 of the guide frame member 433 is recovered by way ofthe recovery groove 435.

Additionally, if control is carried out so that the sprayed amount ofthe atomized slurry 451 is increased gradually along with the ascent ofthe slurry nozzle 441, the slurry 452 is applied to the surface 412 a ofthe negative electrode 412 to a uniform thickness, as shown in FIG. 22F.

In FIG. 22G, with the atomized slurry 451 spraying from the slurrynozzle 441, the slurry nozzle 441 is moved as shown by the arrow [3]from position P2 to position P3.

In FIG. 22H, the slurry nozzle 441 is moved horizontally through thesecond range E2 of from position P2 to position P3 at the maximum heightH2. Consequently, as shown in FIG. 22G, the width W6 of the atomizedslurry 451 sprayed from the slurry nozzle 441 can be kept slightlygreater than the maximum width W2 of the negative electrode 412. By thismeans, the whole maximum width of the negative electrode 412 can becoated with the atomized slurry 451.

The peripheral part of the atomized slurry 451 which projects to outsidethe inner face 434 of the guide frame member 433 is recovered by way ofthe recovery groove 435.

Additionally, to spray the atomized slurry 451 from the slurry nozzle441 at the maximum height H2, if control is carried out so that thesprayed amount of the atomized slurry 451 is increased to a maximum, asshown in FIG. 22H, the slurry 452 is applied to the surface 412 a of thenegative electrode 412 to a uniform thickness.

In FIG. 221, with the atomized slurry 451 spraying from the slurrynozzle 441, the slurry nozzle 441 is moved from position P3 to positionP4 as shown by the arrow [4].

In FIG. 22J, the slurry nozzle 441 descends in a curve with a downwardgradient over the third range E3 of from position P3 to position P4, asshown by the arrow [4]. The end part 441 a of the slurry nozzle 441descends gradually from the maximum height H2 to the minimum height H1along with the movement of the slurry nozzle 441. Consequently, as shownin FIG. 22I, the width W3 of the atomized slurry 451 sprayed from theslurry nozzle 441 can be gradually made smaller in correspondence withthe width (minimum width) Wi of the other end of the negative electrode412. As a result, the atomized slurry 451 does not project more thannecessary from the negative electrode 412.

The peripheral part of the atomized slurry 451 which projects to outsidethe inner face 434 of the guide frame member 433 is recovered by way ofthe recovery groove 435.

Additionally, by control being carried out so that along with thedescent of the slurry nozzle 441 the sprayed amount of the atomizedslurry 451 is gradually decreased, the slurry 452 is applied to thesurface 412 a of the negative electrode 412 to a uniform thickness.

By the slurry nozzle 441 reaching the position P4 in this way, theprocess of applying the slurry 452 ends. On completion of the coatingprocess, the slurry 452 applied to the negative electrode 412 is driedto form the ion exchange film 414 (see FIG. 19).

With the first ion exchange film forming method described above, byimparting a plus charge to the negative electrode 412 and imparting aminus charge to the atomized slurry 451 sprayed from the slurry nozzle441, it is possible to prevent coating nonuniformity of the slurry 452.By this means, the ion exchange film 414 shown in FIG. 19 can be formedto a uniform thickness.

Additionally, by regulating the application area of the slurry 452 withthe guide frame member 433, it is possible to form the slurry 452 to therequired shape simply. Consequently, the edge 414a of the ion exchangefilm 414 can be formed well without difficulty.

Next, a second method of forming the ion exchange film will bedescribed, on the basis of FIG. 23.

In the forming apparatus for implementing the second forming methodshown in FIG. 23, parts the same as in the forming apparatus 430 forimplementing the first forming method shown in FIG. 21 have been giventhe same reference numerals.

The ion exchange film forming apparatus 460 shown in FIG. 23 has a bed431 for placing a negative electrode 412 upon, a guide frame member 463which surrounds the negative electrode 412 when set on this bed 431, andan atomizer 440 provided above this guide frame member 463.

The guide frame member 463 has an inner face 464 of a shape whichfollows the periphery 412 b of the negative electrode 412. A recoverygroove 465 is formed so as to follow this inner face 464. A recoveryhole 466 connecting with this recovery groove 465 is provided. Suctionmeans (not shown) are connected to the recovery groove 465 by way ofthis suction hole 466. The inner face 464 is coated with a coating.

By suction means being connected to the recovery groove 465, becauseslurry collecting in the recovery groove 465 can be drawn out, theslurry can be recovered more easily. Consequently, fuel cellproductivity can be greatly increased.

Although in the foregoing first and second forming methods examples weredescribed wherein a slurry 452 is applied to a negative electrode 412,the same effects can be obtained in applying a slurry 452 to a positiveelectrode 416.

Next, a forming apparatus for implementing a third ion exchange filmmanufacturing method will be described, on the basis of FIG. 24 throughFIG. 26. In the description of this third ion exchange film formingapparatus, parts the same as in the forming apparatus 430 forimplementing the first forming method shown in FIG. 21 have been giventhe same reference numerals.

A third ion exchange film forming apparatus 530 has a bed 431 for theoctagonal negative electrode 412 shown in FIG. 19 to be place upon, aguide frame member 433 which surrounds the negative electrode 412 whenset on this bed 431, and a spraying device 540 disposed above this guideframe member 433.

The bed 431 has plus charge imparting means 432 for imparting a pluscharge to the negative electrode 412.

The guide frame member 433 has an octagonal inner face 434 formed tofollow the periphery 412 b of the negative electrode 412 (see FIG. 19),a recovery groove 435 formed to follow this inner face 434, and arecovery hole 436 formed to connect with this recovery groove 435. Acoating (not shown) has been applied to the inner face 434.

The spraying device 540 has multiple slurry nozzles 541 a through 541 jdisposed in a zigzag. The multiple slurry nozzles 541 a through 541 jare supported movably as shown by an arrow. The slurry nozzles 541 athrough 541 j are each given a minus charge by minus charge impartingmeans 442. That is, the minus charge imparting means 442 imparts a minuscharge to the slurry sprayed from each of the slurry nozzles 541 athrough 541 j.

The slurry nozzles 541 a through 541 j are constructed to beindividually switchable between a state in which they spray slurry and astate in which they do not spray slurry.

Referring to FIG. 25, the multiple slurry nozzles 541 a through 541 jare made up of for example a first slurry nozzle through a tenth slurrynozzle 541 a through 541 j, and these slurry nozzles 541 a through 541 jare disposed in a zigzag shape.

By the third through eighth slurry nozzles 541 c through 541 h amongthese first through tenth slurry nozzles 541 a through 541 j beingbrought to their spraying state over a distance L1, a first area 545located in the center of the negative electrode 412 can be coated.

By the second slurry nozzle 541 b positioned on the outer side of thethird slurry nozzle 541 c and the ninth slurry nozzle 541 i positionedon the outer side of the eighth slurry nozzle 541 h being brought totheir spraying state over a distance L2, second areas 546, 546 on theouter sides of the first area 545 can be coated.

And by the first slurry nozzle 541 a positioned on the outer side of thesecond slurry nozzle 541 b and the tenth slurry nozzle 541 j positionedon the outer side of the ninth slurry nozzle 541 i being brought totheir spraying state over a distance L3, third areas 547, 547 on theouter sides of the second areas 546, 546 can be coated.

FIG. 26 shows in sectional view the ion exchange film forming apparatusshown in FIG. 24 and FIG. 25. First through tenth slurry sprays 551 aresprayed from the first through tenth slurry nozzles 541 a through 541 jdisposed in a zigzag shape as shown in FIG. 25, and a slurry 552 isthereby applied to the negative electrode 412.

Here, the application amounts of respective peripheral parts 551 a ofthe slurry sprays 551 sprayed from the first through tenth slurrynozzles 541 a through 541 j are small. Because of this, to make theapplication amounts of the peripheral parts 551 a equal to theapplication amounts of the central parts 551 b, it is necessary for theapplication amounts of the peripheral parts 551 a to be supplemented.Now, as a method of supplementing the application amounts of theperipheral parts 551 a, making the peripheral parts 551 a, 551 a ofadjacent slurry sprays 551, 551 overlap with each other is conceivable.

However, when the peripheral parts 551 a, 551 a of adjacent slurrysprays 551, 551 interfere with each other, turbulence arises in theinterfering peripheral parts 551 a, 551 a and the slurry 552 cannot beapplied well. To avoid this, the first through tenth slurry nozzles 541a through 541j are arranged in a zigzag shape, to prevent the peripheralparts 551 a, 551 a of adjacent slurry sprays 551, 551 from interferingwith each other.

That is, in an initial state, before the first through tenth slurrynozzles 541 a through 541 j move in the direction shown by the arrows,as shown in FIG. 25, the first through tenth slurry nozzles 541 athrough 541 j are disposed so that the peripheral parts 551 a of theslurry sprays 551 sprayed from the first through tenth slurry nozzles541 a through 541 j do not overlap.

However, when the first through tenth slurry nozzles 541 a through 541 jare moved, the first of the adjacent slurry sprays 551, 551 are appliedto the surface of the negative electrode 412 first, and then theperipheral parts 551 a of the other slurry sprays 551 are applied to theperipheral parts in the applied slurry 552, whereby the peripheral parts551 a, 551 a of the adjacent slurry sprays 551, 551 can be applied in anoverlapping state without turbulence arising in the adjacent slurrysprays 551,551.

As a result of it being possible for peripheral parts 551 a of theslurry sprays 551 to be applied in an overlapping state withoutturbulence arising in the adjacent slurry sprays 551, the appliedamounts of the peripheral parts 551 a of the slurry sprays 551 sprayedfrom the first through tenth slurry nozzles 541 a through 541 j can bemade equal to the applied amounts of the central parts 551 b of therespective slurry sprays 551.

That is, the spacing S1 of the adjacent slurry nozzles 541 a through 541j is set so that coating is possible with the peripheral parts 551 a ofthe slurry sprays 551 sprayed from the second, fourth, sixth, eighth andtenth slurry nozzles 541 b, 541 d, 541 f, 541 h and 541 j overlapping byan amount of overlap S2 with the peripheral parts 551 a of the slurrysprays 551 sprayed from the first, third, fifth, seventh and ninthslurry nozzles 541 a, 541 c, 541 e, 541 g and 541 i.

Next, a third method of forming an ion exchange film for a fuel cellwill be described, on the basis of FIG. 27A through FIG. 27J.

In FIG. 27A, the polygonal negative pole (electrode) 412 is formed fromcarbon paper, and the negative electrode 412 is placed on the bed 431.Then, the plus charge imparting means 432 is adjusted to impart a pluscharge to the negative electrode 412.

In FIG. 27B, the guide frame member 433 is disposed so as to surroundthe negative electrode 412. Then, the minus charge imparting means 442is adjusted to impart a minus charge to the slurry sprays 551 (see FIG.26) to be sprayed from the first through tenth slurry nozzles 541athrough 541j.

In FIG. 27C, when the first through tenth slurry nozzles 541 a through541 j have moved horizontally from a standby position P0 as shown by thearrow [1] and reached a first spraying position P1, the slurry sprays551 (see FIG. 27D) are sprayed from the third through eighth slurrynozzles 541 c through 541 h.

FIG. 27D is a sectional view on the line D-D in FIG. 27C. In FIG. 27D,by the first through tenth slurry nozzles 541 a through 541 j beingmoved horizontally across the negative electrode 412, the peripheralparts 551 a of the slurry sprays 551 sprayed from the third, fifth, andseventh slurry nozzles 541 c, 541 e and 541 g are applied to overlapwith the surfaces coated with the peripheral parts 551 a of the slurrysprays 551 sprayed from the fourth, sixth and eighth slurry nozzles541d, 541 f and 541 h. By this means, the application amounts of theperipheral parts 551 a of the slurry sprays 551 sprayed from the thirdthrough eighth slurry nozzles 541 c through 541 h can be made equal tothe application amounts of the central parts 551 b of those slurrysprays 551.

On the other hand, to keep the application amounts equal, the peripheralparts 551 a of the slurry sprays 551 sprayed from the third and eighthslurry nozzles 541 c and 541 h are made to project to outside the innerface 434 of the guide frame member 433. These projecting peripheralparts 551 a are recovered by way of the recovery groove 435.

In FIG. 27E, when the first through tenth slurry nozzles 541 a through541 j have moved horizontally from a first spraying position P1 as shownby the arrow [2] and reached a second spraying position P2, with theslurry sprays 551 (see FIG. 27F) from the third through eighth slurrynozzles 541 c through 541 h still spraying, slurry sprays 551 aresprayed from the second and ninth slurry nozzles 541 b, 541 i.

FIG. 27F is a sectional view on the line F-F in FIG. 27E. In FIG. 27F,by the first through tenth slurry nozzles 541a through 541ij being movedfurther horizontally across the negative electrode 412, the peripheralparts 551 a of the slurry sprays 551 sprayed from the third, fifth,seventh and ninth slurry nozzles 541 c, 541 e, 541 g and 541 i areapplied to overlap with the surfaces coated with the peripheral parts551 a of the slurry sprays 551 sprayed from the second, fourth, sixthand eighth slurry nozzles 541 b, 541 d, 541 f and 541 h. By this means,the application amounts of the peripheral parts 551 a of the slurrysprays 551 sprayed from the second through eighth slurry nozzles 541 bthrough 541 i can be made equal to the application amounts of thecentral parts 551 b of the slurry sprays 551.

On the other hand, to keep the application amounts equal, the peripheralparts 551 a of the slurry sprays 551 sprayed from the second and ninthslurry nozzles 541 b and 541 i are made to project to outside the innerface 434 of the guide frame member 433. These projecting peripheralparts 551 a are recovered by way of the recovery groove 435.

In FIG. 27G, when the first through tenth slurry nozzles 541 a through541 j have moved horizontally from the second spraying position P2 asshown by the arrow [3] and reached a third spraying position P3, withthe slurry sprays 551 (see FIG. 27H) from the second through ninthslurry nozzles 541 b through 541 i still spraying, slurry sprays 551 aresprayed from the first and tenth slurry nozzles 541 a, 541 j.

FIG. 27H is a sectional view on the line H-H in FIG. 27G. In FIG. 27H,by the first through tenth slurry nozzles 541a through ₅ 41j being movedfurther horizontally across the negative electrode 412, the peripheralparts 551 a of the slurry sprays 551 sprayed from the first, third,fifth, seventh and ninth slurry nozzles 541 a, 541 c, 541 e, 541 g and541 i are applied to overlap with the surfaces coated with theperipheral parts 551 a of the slurry sprays 551 sprayed from the second,fourth, sixth eighth and tenth slurry nozzles 541 b, 541 d, 541 f, 541 hand 541 j. By this means, the application amounts of the peripheralparts 551 a of the slurry sprays 551 sprayed from the first throughtenth slurry nozzles 541 a through 541 j can be made equal to theapplication amounts of the central parts 551 b of those slurry sprays551.

On the other hand, to keep the application amounts equal, the peripheralparts 551 a of the slurry sprays 551 sprayed from the first and tenthslurry nozzles 541 a and 541 j are made to project to outside the innerface 434 of the guide frame member 433. These projecting peripheralparts 551 a are recovered by way of the recovery groove 435.

In FIG. 27I, when the first through tenth slurry nozzles 541 a through541 j have reached a fourth spraying position P4, the spraying of theslurry sprays 551 from the first and tenth slurry nozzles 541 a, 541 iis stopped. As a result, the coating of the third areas 547, 547 ends.

Next, when the first through tenth slurry nozzles 541 a through 541 jhave reached a fifth spraying position P5, the spraying of the slurrysprays 551 from the second and ninth slurry nozzles 541 b, 541 i isstopped. As a result, the coating of the second areas 546, 546 ends.

Then, when the first through tenth slurry nozzles 541 a through 541 jhave reached a sixth spraying position P6, the spraying of the slurrysprays 551 from the third through eighth slurry nozzles 541 c through541 h is stopped. As a result, the coating of the first area 545 ends.

With the ending of the coating of the first area 545, the process ofapplying the slurry 552 to the negative electrode 412 is completed.After the completion of the application process, by the slurry 552applied to the negative electrode 412 being dried, the ion exchange film414 (see FIG. 19) is formed.

With this third forming method, by using multiple slurry nozzles 541 athrough 541 j, when some of the slurry nozzles fall outside theperiphery 412b of the negative electrode 412, no slurry sprays 551 aresprayed from the slurry nozzles having fallen outside. By this means,because it is possible to avoid the slurry 552 being applied to theareas 554 outside the periphery 412 b of the negative electrode 412(i.e. the corner parts of the guide frame member 433), the time requiredfor recovering slurry after the application can be shortened.

Because slurry sprays 551 are sprayed and applied to the negativeelectrode 412 individually from multiple slurry nozzles 541 a through541 j, the slurry spray amounts from the respective slurry nozzles 541 athrough 541 j can be adjusted individually. As a result, without makingthe spraying accuracy of the slurry nozzles 541 a through 541 junnecessarily high, just by adjusting the slurry spray amounts from therespective slurry nozzles 541 a through 541 j individually, it ispossible to make the surface of the slurry 552 flat relatively easily.

Also, by imparting a plus charge to the negative electrode 412 andimparting a minus charge to the slurry sprayed from the first throughtenth slurry nozzles 541 a through 541 j, it is possible to preventcoating nonuniformity of the slurry 552. By this means, the ion exchangefilm 414 shown in FIG. 19 can be formed to a uniform thickness.

Furthermore, as explained with reference to FIG. 27C through FIG. 27H,in the spraying of the slurry sprays 551 from the first through tenthslurry nozzles 541 a through 541 j, the peripheral parts 551 a of theslurry sprays 551 sprayed from the first, third, fifth, seventh andninth slurry nozzles 541 a, 541 c, 541 e, 541 g and 541 i can be appliedto overlap with the surfaces coated with the peripheral parts 551 a ofthe slurry sprays 551 sprayed from the second, fourth, sixth eighth andtenth slurry nozzles 541 b, 541 d, 541 f, 541 h and 541 j. By thismeans, the slurry 551 sprayed from the first through tenth slurrynozzles 541 a through 541 j can be applied uniformly to the negativeelectrode 412 and the thickness of the ion exchange film 414 shown inFIG. 19 can be made uniform.

Additionally, by regulating the application areas (the first, second andthird areas) 545, 546, 547 of the slurry 552 with the guide frame member433, it is possible to form the slurry 552 to the required shape simply.Consequently, the edge 414 a of the ion exchange film 414 can be formedwell without difficulty.

FIG. 28A and FIG. 28B are views comparing the characteristics of a fuelcell ion exchange film forming method according to the invention with acomparison example. FIG. 28A shows the comparison example, and FIG. 28Bshows as an embodiment the slurry nozzles 541 h, 541 i, 541 j, which aresome of the slurry nozzles 541 a through 541 j.

In the comparison example shown in FIG. 28A, slurry nozzles 561 athrough 561 c are disposed on straight line 563, and when slurry sprays562 are sprayed from the slurry nozzles 561 a through 561 c, peripheralparts 562 a of adjacent slurry sprays 562 interfere with each other andturbulence arises in the peripheral parts 562 a of the slurry sprays562. Consequently, because it is not possible for the slurry to beapplied uniformly even by moving the slurry nozzles 561 a through 561 cas shown with the arrows, the thickness of the ion exchange film cannotbe made uniform.

In FIG. 28B, the slurry nozzles 541 h, 541 i and 541 j are disposed in azigzag shape so that the peripheral parts 551 a of the slurry sprays 551do not interfere with each other.

When the slurry nozzles 541 h, 541 i and 541 j move horizontally asshown by the arrows [5], first the surface of the negative electrode 412is coated with the peripheral parts 551 a of the slurry sprays 551sprayed from the slurry nozzles 541 h and 541 j, and then the peripheralparts 551 a of the slurry sprays 551 sprayed from the slurry nozzle 541i are applied to overlap. Thus the slurry 552 (see FIG. 27J) can beapplied uniformly, and the thickness of the ion exchange film 414 shownin FIG. 19 can be made uniform.

FIG. 29 shows an ion exchange film forming apparatus for implementing afourth ion exchange film forming method. In the description of thisfourth forming method, parts the same as parts of the forming apparatusfor implementing the third forming method shown in FIG. 26 have beengiven the same reference numerals.

An ion exchange film forming apparatus 570 has a bed 431 for placing anegative electrode 412 upon, a guide frame member 573 which surroundsthe negative electrode 412 when set on this bed 431, and a sprayingdevice 540 disposed above this guide frame member 573.

The guide frame member 573 has an inner face 574 formed so as to followthe periphery 412 b of the negative electrode 412, a recovery groove 575formed so as to follow this inner face 574, and suction passages 576formed so as to connect with this recovery groove 575. By suction meansnot shown in the drawing, slurry collected in the recovery groove 575 isrecovered through the suction passages 576. A coating has been appliedto the inner face 574.

By connecting suction means to the recovery groove 575 like this, slurrycollecting in the recovery groove 575 can be drawn out, and the slurrycan be more easily recovered. Consequently, fuel cell productivity canbe increased further.

Although in the third and fourth ion exchange film forming methodsexamples were described wherein a slurry 552 was applied to a negativeelectrode 412, it is not limited to this, and a slurry 552 mayalternatively be applied to a positive electrode 416.

FIG. 30 is an exploded perspective view of a fuel cell having a fuelcell electrode according to an eighth embodiment of the invention.

A fuel cell unit 600 of this embodiment is made up of a plurality of (inthis example, two) fuel cells 611, 611. Each fuel cell 611 has anegative electrode plate 612, an ion exchange film 615, a positiveelectrode plate 616 stacked against the ion exchange film 615, anegative electrode side flow channel plate 621 disposed on the outerside of the negative electrode plate 612, and a positive electrode sideflow channel plate 624 disposed on the outer side of the positiveelectrode plate 616. The negative electrode 612 is made up of a negativesubstrate 613 and a negative pole (electrode) 614. The positiveelectrode plate 616 is made up of a positive substrate 617 and apositive pole (electrode) 618.

A plurality of these fuel cells 611 are provided with separators 626between them to constitute the fuel cell unit 600.

By the negative electrode side flow channel plate 621 being stackedagainst the negative substrate 613 and flow channels 621a in thenegative electrode side flow channel plate 621 being covered by thenegative substrate 613, hydrogen gas flow passages 622 are formed. Andby the positive electrode side flow channel plate 624 being stackedagainst the positive substrate 617 and flow channels 624a in thepositive electrode side flow channel plate 624 being covered by thepositive substrate 617, oxygen gas flow passages 625 are formed.

By hydrogen gas being supplied to the hydrogen gas flow passages 622,hydrogen molecules (H₂) are adsorbed onto a catalyst included in thenegative electrode 614. And by oxygen gas being supplied to the oxygengas flow passages 625, oxygen molecules (O₂) are adsorbed onto acatalyst included in the positive electrode 618. As a result, electrons(e⁻) flow as shown by the arrow and a current is produced. When thecurrent arises, product water (H₂O) is obtained from the hydrogenmolecules (H₂) and oxygen molecules (O₂).

FIG. 31 shows a cross-section of the negative electrode plate 612 andthe ion exchange film 615 shown in FIG. 30. The negative electrode plate612 is formed by providing the negative electrode 614 on the negativesubstrate 613. A surface part 613 a of the negative substrate 613projecting from the periphery of the negative electrode 614 is coveredby the ion exchange film 615.

The negative substrate 613 is a sheet of carbon paper made of carbon,and has the negative electrode 614 provided on one side 613 b thereof. Acatalyst is included in this negative electrode 614, and hydrogenmolecules (H₂) are adsorbed onto this catalyst.

The positive substrate 617 shown in FIG. 30 is a sheet of carbon papermade of carbon like this negative substrate 613, and has the positiveelectrode 618 on one side thereof. A catalyst is included in thispositive electrode 618, and oxygen molecules (O₂) are adsorbed onto thiscatalyst.

The ion exchange film 615 is obtained by applying a resin solution (forexample an HC polymer solution) to the negative electrode 614 and thesurface part 613 a of the negative substrate 613 which projects from thenegative electrode 614, and then drying the resin solution.

Next, a method of forming the ion exchange film shown in FIG. 31 will bedescribed, on the basis of FIG. 32A through FIG. 32G.

In FIG. 32A, a negative electrode plate (negative electrode) 612 made byapplying a negative pole (electrode) 614 to a negative substrate(substrate) 613 is prepared, and this negative electrode plate 612 isplaced on a bed 631.

In FIG. 32B, by an outer side regulating wall member 632 being disposedalong the periphery 612 a of the negative electrode plate 612, thenegative electrode plate 612 is surrounded with this outer sideregulating wall member 632. This outer side regulating wall member 632is made up of two divided left and right outer side regulating wallmembers 633, 634. After the negative electrode plate 612 is surroundedwith the two outer side regulating wall members 633, 634, coatings 635,635 are applied to the inner walls 633a, 634a of the outer sideregulating wall members 633, 634.

Then, a spraying device 638 is disposed above the negative electrodeplate 612 (for example, above one end 613C of the negative substrate613. After that, plus charge imparting means 641 is adjusted to impart aplus charge to the negative electrode plate 612, and minus chargeimparting means 642 is adjusted to impart a minus charge to the resinsolution sprayed from the nozzle 639 of the spraying device 638.

In FIG. 32C, a resin solution included in a gas is sprayed from thenozzle 639 of the spraying device 638. This atomized resin liquid 645 isgiven a minus charge by the minus charge imparting means 642. By thespraying device 638 being moved across the surface of the negativeelectrode plate 612 in this state as shown by the arrow [1], the resinsolution 646 is applied to the surface part 613a of the negativesubstrate 613 from the end 613 c of the negative substrate 613 to oneend 614 a of the negative electrode 614.

As the resin solution 646 is applied, by a minus charge being applied tothe atomized resin liquid 645 and a plus charge being applied to thenegative electrode plate 612, the atomized resin liquid 645 can beapplied to the surface part 613 a of the negative substrate 613 wellwithout unevenness.

In FIG. 32D, the spraying device 638 is moved further as shown by thearrow [1]. At this time, a spray pressure of the atomized resin liquid645 acts on the edge of the end 614 a of the negative electrode 614, butbecause a gas is included in the atomized resin liquid 645, the spraypressure of the atomized resin liquid 645 can be kept down. By thismeans, when the resin solution 646 is applied to the edge of the end 614a of the negative electrode 614, the spray pressure, i.e. the shearforce, acting on the edge of the end 614 a of the negative electrode 614can be kept small. Consequently, the surface layer 614 b of the negativeelectrode 614 is prevented from shifting horizontally as it does inrelated art.

In FIG. 32E, the spraying device 638 is moved further as shown by thearrow [1]. At this time, the spray pressure of the atomized resin liquid645 acts on the surface layer 614b of the negative electrode 614, butbecause the spray pressure acts vertically on the surface layer 614 b ofthe negative electrode 614, the surface layer 614 b of the negativeelectrode 614 is prevented from shifting horizontally as it does inrelated art.

Also, when the spraying device 638 reaches the other end 614 c of thenegative electrode 614, the spray pressure of the atomized resin liquid645 acts on the edge of the other end 614 c of the negative electrode614, but because a gas is included in the atomized resin liquid 645, thespray pressure of the atomized resin liquid 645 can be kept down. Bythis means, in applying the resin solution 646 to the edge of the otherend 614 c of the negative electrode 614, the spray pressure, that is,the shear force, acting on the edge of this end 614 c of the negativeelectrode 614 can be kept small. Consequently, the surface layer 614 bof the negative electrode 614 is prevented from shifting horizontally asit does in related art.

In FIG. 32F, by the spraying device 638 moving from the end 614 c of thenegative electrode 614 to the end 613 d of the negative substrate 613,the resin solution 646 is applied to the surface part 613 a between theend 614 c of the negative electrode 614 and the end 613 d of thenegative substrate 613. This completes the coating process.

As a result of the negative electrode plate 612 being surrounded withthe outer side regulating wall member 632, when the resin solution 646is applied, the resin solution 646 is formed to follow the outer sideregulating wall member 632. Consequently, the periphery of the resinsolution 646, i.e. the periphery 615 a of the ion exchange film 615shown in FIG. 31, can be formed well.

By imparting a plus charge to the negative electrode plate 612 andimparting a minus charge to the atomized resin liquid 645 sprayed fromthe spraying device 638, it is possible to prevent coating unevenness ofthe resin solution 646 and apply the resin solution 646 to a uniformthickness.

In cases where by just moving the spraying device 638 as shown in FIG.32D in the direction of the arrow [1] it would be difficult to apply theresin solution 646 to a uniform thickness, by applying it again with thespraying device 638 where the thickness of the resin solution 646 isthin, the resin solution 646 can be applied to a uniform thickness.

Also, as another method, by adjusting the rate of delivery of theatomized resin liquid 645 from the spraying device 638, the resinsolution 646 can be applied to a uniform thickness. For example, incases where there are parts where the thickness of the resin solution646 is thin when the atomized resin liquid 645 is applied, by deliveringmore of the atomized resin liquid 645 at those parts, the resin solution646 can be applied to a uniform thickness.

After completion of the coating process, the spraying device 638 iswithdrawn from above the resin solution 646. Then, by cooling the outerside regulating wall member 632 (the left and right outer sideregulating wall members 633, 634), the peripheral part 646 a of theresin solution 646 is cooled and to a certain extent set. In this state,as shown in FIG. 32G the left and right outer side regulating wallmembers 633, 634 are removed from the bed 631 as shown by the arrows[2].

Because the coatings 635, 635 have been applied to the inner walls 633a, 634 a of the left and right outer side regulating wall members 633,634, their detachability from the resin solution 646 can be kept good.

Additionally, by the peripheral part 646 a of the resin solution 646being cooled and somewhat set, when the outer side regulating wallmember 632 (the left and right outer side regulating wall members 633,634) is removed, deformation of the peripheral part 646 a of the resinsolution 646 can be prevented.

Although in the fifth ion exchange film forming method an example wasdescribed wherein the spraying device 638 was moved from one end of thenegative electrode plate 612 toward the other end, it is not limited tothis, and it is also possible for the coating to be carried out by thespraying device 638 being moved from the center of the spraying device638 (that is, the center of the negative electrode 614) toward the endsor by some other movement method.

Although in the forming method described above an example was describedwherein the resin solution 646 was applied to a negative electrode plate612, it is not limited to this, and the same effects can be obtained inapplying the resin solution 646 to a positive electrode plate 616.

INDUSTRIAL APPLICABILITY

In the fuel cell electrode manufacturing method of this invention,because the ion exchange film is made a solution, and a solution formaking the positive electrode layer, the solution for making the ionexchange film and a solution for making the negative electrode layer areeach applied in an undried state, each solution permeates the filmapplied before it and areas of defective intimacy do not arise at theinterfaces of the layers. Also, because the ion exchange film is appliedusing a solution, it can be made thin and the electrode structure can bemade as small as possible, and it is useful in the manufacture of fuelcells used in various industries.

1. A fuel cell electrode manufacturing method, comprising: a step ofapplying a solution for making a first electrode of positive andnegative electrodes of a fuel cell to a sheet to form a first electrodelayer; a step of, before this electrode layer has dried, applying asolution for making an ion exchange film to this first electrode layerto form an ion exchange film; a step of, before this ion exchange filmhas dried, applying a solution for making the second electrode to theion exchange film to form a second electrode layer; and a step ofhardening the first electrode layer, the second electrode layer and theion exchange film by drying them.
 2. A fuel cell electrode manufacturingmethod according to claim 1, wherein the drying is carried out without aload being applied.
 3. A fuel cell electrode manufacturing methodaccording to claim 1, wherein, of the electrode layers of the positiveand negative electrodes, the negative electrode layer is formed belowthe ion exchange film and the positive electrode layer is formed abovethe ion exchange film.
 4. A fuel cell electrode manufacturing methodaccording to claim 1, wherein the solution for making the positiveelectrode is applied in a spray state.
 5. A fuel cell electrodemanufacturing method according to claim 1, wherein the drying is carriedout by heating from the insides of the electrodes with far infraredradiation so as to prevent excessive penetration of the solution formaking the ion exchange film into the electrodes.
 6. A fuel cellelectrode manufacturing method according to claim 1, wherein in thesolutions for making the positive and negative electrodes a solvent witha higher vaporization temperature than a solvent used in the solutionfor making the ion exchange film is used.
 7. A fuel cell electrodemanufacturing method according to claim 1, wherein the first electrodelayer is divided into two layers, a first layer on the side away fromthe ion exchange film and a second layer on the side in contact with theion exchange film, and the porosity of the second layer is lower thanthe porosity of the first layer.
 8. A fuel cell electrode manufacturingmethod according to claim 7, wherein the porosity of the second layer is70% to 75%.
 9. A fuel cell electrode manufacturing method according toclaim 7, wherein the porosity of the first layer is 76% to 85%.
 10. Afuel cell electrode manufacturing method according to claim 7, whereinto make the porosity of the second layer lower than the porosity of thefirst layer, a solution for making the second layer is applied with ahigher atomization energy than a solution for making the first layer.11. A fuel cell electrode manufacturing method according to claim 7,wherein to make the porosity of the second layer lower than the porosityof the first layer, the size of electrode particles included in asolution for making the second layer is made smaller than the size ofelectrode particles included in a solution for making the first layer,to make the density of the solution for making the second layer higherthan the density of the solution for making the first layer.
 12. A fuelcell electrode manufacturing method according to claim 1, comprising astep of forming a first electrode side diffusion layer before the stepof forming the first electrode layer, the first electrode layer thenbeing formed while the first electrode side diffusion layer is not yetdry, and a step of forming a second electrode side diffusion layer afterthe second electrode layer is formed, the second electrode sidediffusion layer being formed while the second electrode layer is not yetdry.
 13. A fuel cell electrode manufacturing method according to claim12, wherein the first electrode side diffusion layer is made up of apositive electrode side carbon paper and a positive electrode sidebinder layer, and the second electrode side diffusion layer is made upof a negative electrode side carbon paper and a negative electrode sidebinder layer.
 14. A fuel cell electrode manufacturing method accordingto claim 13, wherein a solution for making the positive electrode sidebinder layer includes water as a solvent and includes a water repellentlow-melting-point resin whose melting point is not greater than 150° C.15. A fuel cell electrode manufacturing method according to claim 14,wherein the low-melting-point resin is a vinylidenefluoride/tetrafluoroethylene/hexafluoropropylene copolymer.
 16. A fuelcell electrode manufacturing method according to claim 14, wherein inthe stacking of the positive electrode side diffusion layer, thepositive electrode layer, the ion exchange film, the negative electrodelayer and the negative electrode side diffusion layer, a first binderlayer is formed on a first carbon paper of the negative electrode sidediffusion layer and the positive electrode side diffusion layer, a firstof the positive and negative electrode layers is formed on the firstbinder layer, the ion exchange film is formed on this first electrodelayer, the second electrode layer is formed on this ion exchange film, asecond binder layer is formed on this second electrode layer, and asecond carbon paper is placed on this second binder layer, and anadhesive resin having excellent adhesion is included in a solution formaking the second binder layer.
 17. A fuel cell electrode manufacturingmethod according to claim 16, wherein the adhesive resin is an ionexchange resin.
 18. A fuel cell electrode manufacturing method accordingto claim 13, wherein a solution for making the positive electrode sidebinder layer includes an organic solvent and includes a resin which issoluble in this organic solvent and is water repellent.
 19. A fuel cellelectrode manufacturing method according to claim 18, wherein the waterrepellent resin soluble in the organic solvent is a resin chosen fromamong the group consisting of vinylidenefluoride/tetrafluoroethylene/hexafluoropropylene copolymers,polyvinylidene fluoride, fluoro-olefin/hydrocarbon-olefin copolymers,fluoro-acrylate copolymers, and fluoro-epoxy compounds.
 20. A fuel cellelectrode manufacturing method according to claim 12, comprising a stepof, after forming the first diffusion layer, flattening the upper faceof the first diffusion layer by pressing the upper face of the firstdiffusion layer before the first diffusion layer has dried.
 21. A fuelcell electrode manufacturing method according to claim 20, wherein thefirst diffusion layer is made by applying a binder to a sheet with asprayer.
 22. (canceled)
 23. (canceled)
 24. (canceled)
 25. (canceled) 26.(canceled)
 27. (canceled)
 28. (canceled)
 29. A fuel cell electrode,comprising: a first electrode layer, formed by applying a solution formaking a first electrode of positive and negative electrodes of a fuelcell to a sheet; an ion exchange film, formed by applying a solution formaking an ion exchange film to the first electrode layer before thefirst electrode layer has dried; and a second electrode layer, formed byapplying a solution for making the second electrode to the ion exchangefilm before the ion exchange film has dried, wherein the first electrodelayer is made up of a first layer on the side away from the ion exchangefilm and a second layer on the side in contact with the ion exchangefilm, and the porosity of the second layer is lower than the porosity ofthe first layer.
 30. A fuel cell electrode according to claim 29,wherein the porosity of the second layer is 70% to 75%.
 31. A fuel cellelectrode according to claim 29, wherein the porosity of the first layeris 76% to 85%.
 32. A fuel cell electrode according to claim 29, whereinto make the porosity of the second layer lower than the porosity of thefirst layer, the size of electrode particles included in a solution formaking the second layer is made smaller than the size of electrodeparticles included in a solution for making the first layer.